Is It Safe to Drink Canned Soda Left in a Hot Car?

A single can of soda that has been sitting in your hot car for a few hours is not going to poison you. The drink inside remains microbiologically safe because commercially sealed cans are sterile environments, and the temperatures a car reaches, while uncomfortable for people, are not high enough to compromise the can’s structural seal in the short term. That said, heat does quietly accelerate several chemical processes inside the can, and the longer a canned beverage stays hot, the more those changes add up. The real question is less about a one-time forgotten can and more about what happens when heat exposure stretches from hours into days or weeks.

What Heat Does to the Can’s Inner Lining

Most aluminum beverage cans are coated on the inside with a thin layer of resin, historically an epoxy that contains bisphenol A (BPA). That lining exists to keep the acidic soda from touching the metal directly, preventing both corrosion and off-flavors. The trade-off is that the lining itself can release trace amounts of BPA into the liquid, and heat is one of the strongest accelerators of that release. A review of the research on BPA migration found that high temperature, low pH (acidity), exposure to sunlight, and prolonged contact time all increase how much BPA moves from the container into the food or drink inside it.¹ A car interior on a summer day can easily hit 50–70°C (roughly 120–160°F), and a can sitting in direct sun on the dashboard can get even hotter. Those are exactly the conditions that push BPA migration upward.

How much BPA are we actually talking about? One laboratory study that tested aluminum cans with epoxy linings at elevated temperatures found BPA levels around 68 nanograms per can.² That number is extraordinarily small in absolute terms. Another study that looked specifically at canned beverages stored at 40°C (104°F) for up to 90 days found an average BPA concentration of about 0.58 micrograms per liter, with the highest reading reaching 2.2 micrograms per liter in cola stored for three months.³ Cola showed the highest migration partly because of its very low pH, which works together with heat to pull more BPA from the lining. Even the worst-case number in that study was well below the limits set by U.S. and European food-safety regulators, though it is worth noting that scientific debate about BPA’s safety at low doses continues and some researchers argue the regulatory limits themselves are too generous.

BPA-Free Linings Are Not the Whole Answer

Many beverage manufacturers have transitioned to BPA-free can linings in recent years, often using alternative bisphenols such as BPS (bisphenol S) or BPF (bisphenol F). If you are picturing a clean break from the problem, the reality is more nuanced. The same study that tracked BPA at 40°C also measured BPS and BPF migration and found both present in canned beverages, though at lower average concentrations than BPA.³ The same pattern held: higher temperatures and longer storage times meant more migration, and acidic drinks like cola and citrus-flavored sodas drew out more of these compounds than less acidic beverages. The migration levels of BPS and BPF were considerably lower than those of BPA, but these substitute chemicals have less long-term safety data behind them, which leaves an open question about whether “BPA-free” on a label actually means “nothing to think about.”

Aluminum Leaching From the Can Wall

The protective lining inside a can is not a perfect barrier, and it can develop microscopic imperfections during manufacturing, shipping, or simply from sitting on a shelf. Where those tiny gaps exist, the acidic soda contacts the aluminum directly. Over time, and especially in acidic drinks, aluminum dissolves into the liquid. Research going back decades has confirmed that aluminum content in canned soft drinks increases steadily over storage time, driven primarily by the acid concentration and low pH of the beverage.⁴

A more recent study examining old versus fresh canned beverages found that older cans had significantly more aluminum in the liquid, and the beverage itself had become slightly more acidic over time, likely accelerating the corrosion cycle further.⁵ Heat speeds up this process for the same reason it speeds up most chemical reactions: molecules move faster and react more readily. A can that spends a single hot afternoon in your car will pick up a trivial amount of aluminum. A case of soda stored in a hot garage for an entire summer is a different story. The aluminum levels are still unlikely to exceed regulatory limits for any single serving, but the cumulative effect matters if you are routinely drinking beverages stored in less-than-ideal conditions.

For context, you get far more dietary aluminum from common foods like baked goods (which use aluminum-containing leavening agents), processed cheese, and tea than you would from a warm can of soda. The contribution from a can, even a heat-stressed one, is small in the bigger picture of your total aluminum intake.

Benzene Formation in Certain Sodas

This one catches people off guard because it sounds alarming on its face: some sodas can form benzene, a known human carcinogen, inside the can. The mechanism is specific. When a beverage contains both a benzoate preservative (sodium benzoate or potassium benzoate) and ascorbic acid (vitamin C) or erythorbic acid, a chemical reaction can produce benzene at trace levels. A survey by the U.S. FDA found benzene at nanogram-per-gram levels in certain beverages containing this combination, and the research confirmed that elevated temperatures and light exposure stimulate the reaction, while sugar can partially inhibit it.⁶

The practical implications here are modest but real. Most major soda brands have reformulated to avoid the benzoate-plus-ascorbic-acid combination, largely in response to the FDA’s findings in the mid-2000s. But some smaller brands, flavored waters, and citrus-flavored drinks still use both ingredients. If you are the type of person who stocks up on cases of soda and leaves them in a vehicle or a hot shed, drinks containing both benzoate preservatives and vitamin C are the worst candidates for that treatment. Checking the ingredient label is straightforward, and for the vast majority of mainstream colas and lemon-lime sodas, this specific concern does not apply.

Will the Can Explode?

Carbonated beverages are pressurized, and that pressure increases as temperature rises. Carbon dioxide becomes less soluble in liquid as it warms, so more of it escapes into the headspace of the can, pushing up internal pressure. On a particularly brutal day, where car interior temperatures climb above 55°C (about 130°F), cans occasionally burst, especially if they have been shaken or have a subtle manufacturing defect in the seal. The mess is the main consequence: sticky soda sprayed across your upholstery and trunk lining.

A can that does not burst but gets very hot will still hiss aggressively when you open it, because there is more gas in the headspace than at room temperature. This is not a safety hazard to the drinker. If you let it cool back down before opening, most of the CO₂ re-dissolves and the drink returns to something close to its original carbonation. A can that has experienced repeated heating and cooling cycles will gradually lose carbonation over time, though, because each warm-up pushes a small amount of gas past the seal permanently. That is why a can from a hot car often tastes flat even after it cools.

Why the Soda Tastes Wrong

Even setting aside the chemistry of BPA, aluminum, and benzene, heat degrades the flavor of soda in ways you can plainly taste. Artificial sweeteners in diet sodas are sensitive to heat and break down faster at elevated temperatures, which can produce off-flavors or reduce sweetness. The volatile flavor compounds that give each brand its distinctive taste are also more prone to degradation or loss when the liquid gets warm. Citrus-flavored sodas tend to suffer the most because their flavoring compounds are among the least heat-stable.

Caramel-colored colas, meanwhile, are somewhat more forgiving because their flavor profile relies on compounds that are already the product of high-heat processes (caramelization itself is a cooking reaction). But even a cola stored hot for weeks will taste noticeably stale compared to one kept at room temperature. None of this makes the drink unsafe. It makes it unpleasant, which for most people is the limiting factor long before any toxicological concern becomes relevant.

How Cans Compare to Plastic Bottles in Heat

If you are choosing between leaving a can or a plastic bottle of soda in your car, both have downsides. The chemical migration story is broadly similar for both packaging types: heat and time increase the transfer of unwanted compounds from the container into the drink, and acidic beverages draw out more than neutral ones.⁷ Plastic bottles, particularly those made from PET (the most common type for soft drinks), can release their own set of migrants, including antimony and various plasticizers, especially when heated. And because plastic is more permeable than aluminum, plastic bottles also lose carbonation faster in the heat and allow more oxygen in, which accelerates flavor degradation.

Glass, for what it is worth, is the most inert container for a hot environment. It does not leach anything into the drink. But glass bottles are heavier, breakable, and uncommon for soda outside of certain markets, so the practical choice for most people is between cans and plastic. If you know a beverage is going to sit in a hot car for a while, a can is arguably the slightly better bet because the aluminum wall blocks light completely (reducing the benzene-formation pathway and UV-driven flavor breakdown) and retains carbonation more effectively than a plastic bottle. But the differences are marginal for a one-time event.

Acidity Matters More Than You Think

A theme running through all the research on canned beverages and heat is that the pH of the drink itself is a major player. Cola, with a pH typically around 2.5, is significantly more acidic than, say, a root beer at pH 4 or a ginger ale hovering near 3.5. That acidity amplifies every heat-driven process: more BPA and BPS migration from the lining, more aluminum dissolution from the can wall, and in drinks with the right preservative combination, more benzene formation.³ The research consistently shows that cola and citrus-flavored sodas are the worst performers in heat-stress scenarios, while less acidic drinks fare better.

This does not mean you should avoid cola. It means that if you routinely buy cases of soda and store them somewhere that gets hot, picking a less acidic variety, or simply moving the case indoors, makes a measurable difference in the chemical quality of what you eventually drink. And it means that the stray can of lemon-lime soda forgotten under your passenger seat for a month in August is a worse situation, chemically speaking, than the same timeline for a cream soda or a lightly flavored sparkling water.

Microbiological Safety and Sealed Cans

One concern you can mostly set aside is bacteria. Commercially canned beverages are filled and sealed under conditions designed to prevent microbial contamination, and the combination of low pH, preservatives, and an airtight seal makes the inside of a soda can a hostile environment for microorganisms.⁸ Heat does not change that equation as long as the can remains sealed and undamaged. You are not going to grow mold or bacteria inside a sealed can of soda regardless of how hot it gets.

The exception is a can that has been compromised: a popped tab, a dent deep enough to breach the lining, or a pinhole leak. A damaged can in a hot environment is a different proposition entirely. If you find a can that looks swollen, leaks when tilted, or makes an unusual sound when you shake it, discard it. The food-safety concern with damaged cans is real, even though it has nothing to do with temperature specifically.

Storing Beverages in Vehicles

Car interiors can reach surprisingly extreme temperatures. On a 35°C (95°F) day, the dashboard surface can exceed 70°C (158°F) within an hour, and even the floor or trunk will climb well above ambient. If you regularly keep drinks in your vehicle, a few habits make a meaningful difference. Store cans in the trunk rather than on the seat or dashboard, since trunk temperatures stay somewhat lower and the cans are shielded from direct sunlight. Bring drinks inside at the end of the day rather than leaving them overnight during a heat wave. And avoid buying large quantities to stockpile in a garage or shed that is not climate-controlled during summer months. The research is clear that duration of heat exposure matters more than peak temperature: 90 days at a moderate 40°C produced the highest migration levels of BPA in canned cola, suggesting that chronic warmth is worse than a single scorching afternoon.³

For the occasional forgotten can, the calculus is simple. If it looks normal, is not bulging, and was only in the heat for a day or two, you can drink it. It might taste flat or slightly off, and it will have marginally higher levels of various migrants than it would have at room temperature, but those levels remain well within what regulators consider safe for a single serving. If the can has been baking in your car for weeks, the taste alone will probably convince you to toss it, and that instinct is a reasonable one to follow.

1
PubMed Central. Bisphenol A release from food and beverage containers – A review
2
Letters in Applied NanoBioScience. Leaching of BPA from Baby Feeding Bottle, Aluminium Can and Thermal Printed Paper: Application of Acridine Orange Oxidation Method to Estimate BPA
3
PubMed. Quantitative evaluation of bisphenol A, S, and F migration from canned beverages: impact of storage conditions and associated health risk assessment
4
PubMed. Aluminium content of soft drinks from aluminium cans
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Food Packaging and Shelf Life. Metal content in soft drinks depending on packaging and storage time
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PubMed. Survey results of benzene in soft drinks and other beverages by headspace gas chromatography/mass spectrometry
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PubMed Central. Food Packaging and Chemical Migration: A Food Safety Perspective
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PubMed Central. Health safety of soft drinks: contents, containers, and microorganisms