No, you should not drink from a bulging soda can. The USDA’s food safety guidance is straightforward: do not use any swollen cans, and discard them. A can that’s visibly puffed out or deformed means something has generated excess gas inside, and while the cause might be harmless, it can also signal contamination or chemical breakdown you can’t detect by looking.
Why Soda Cans Bulge
A soda can is already pressurized with carbon dioxide, which is what gives it that familiar fizz. For the can to bulge beyond its normal shape, something has to push the internal pressure well past what the container was designed to hold. There are three main reasons this happens.
Heat exposure. Leaving a can in a hot car, near a stove, or in direct sunlight causes the liquid and dissolved gas inside to expand. The pressure builds until the can deforms outward. In extreme cases, cans stored in high heat can actually explode.
Freezing. Water expands as it freezes, so a soda can left in a freezer or outdoors in winter can swell and even crack at the seams. If you accidentally froze a can and it’s still sealed with no leaks, the contents are generally not contaminated, just physically stressed. That said, freezing can compromise the seal integrity in ways that aren’t visible, so caution is still warranted.
Microbial or chemical reactions. This is the concerning one. Spoilage bacteria and yeast can produce gas inside a sealed container, pressurizing it from within. Separately, the acids naturally present in soda can react with the aluminum or steel of the can itself, generating hydrogen gas. This chemical process is more likely when the protective lining inside the can is damaged or degraded. Either way, the result is a compromised product you shouldn’t consume.
The Botulism Question
Many people associate bulging cans with botulism, and for good reason. The bacterium that causes botulism thrives in low-oxygen, sealed environments and produces gas as it grows. Bulging is one of the classic warning signs the USDA lists for possible botulism contamination, alongside leaking, foul odors, and spurting liquid when opened.
The good news is that commercially produced sodas are quite acidic, typically with a pH well below 4.6. The botulism bacterium cannot grow below a pH of 4.6, which means standard carbonated soft drinks are a very unlikely environment for it. This is the same reason most fruits and pickled foods are considered lower-risk for botulism.
That said, “very unlikely” isn’t the same as impossible. If the product has been tampered with, improperly manufactured, or if you’re dealing with a flavored or low-acid beverage that looks like soda but has a different formulation, the risk profile changes. The pH protection only works if the acidity is intact.
How to Tell What Caused the Bulge
If you pulled a can out of your freezer and it’s swollen, you can probably figure out what happened. But in most situations, you won’t know why a can is bulging just by looking at it. There’s no reliable way to visually distinguish a heat-expanded can from one that’s swollen due to microbial contamination or internal chemical reactions.
There are a few additional red flags that signal the contents are definitely unsafe:
- Hissing or spurting when opened. If the can releases pressure violently or the liquid sprays out, the USDA considers this a sign the food is unsafe. Don’t taste it.
- Unusual smell. Any off or foul odor when you open the can means something has gone wrong inside.
- Cloudiness or unusual color. Soda should look the way you expect it to look. Murky liquid or visible particles are signs of spoilage.
- Damage to the can. Deep dents, especially along the seams, rust, or any signs of leaking all compromise the seal and increase the chance of contamination.
How to Safely Dispose of a Bulging Can
A pressurized, bulging can poses a physical hazard beyond what’s inside it. The excess pressure means it could burst if punctured, dropped, or exposed to more heat. Don’t try to open it the way you’d open a normal soda.
Place the can in a plastic bag to contain any leakage, and dispose of it in your regular trash. Keep it away from heat sources and direct sunlight while you’re handling it. If the can is severely distorted or feels like it’s under significant pressure, handle it gently and at arm’s length. Don’t attempt to puncture or crush it to release the pressure.
The Bottom Line on Bulging Cans
The cost of a single soda is not worth the risk. Even in the best-case scenario, where the bulge was caused by simple heat exposure, the product has been stored outside its intended conditions and the flavor will likely be off. In the worst case, you could be drinking something contaminated with harmful bacteria or chemical byproducts from the can’s own materials breaking down. The USDA doesn’t hedge on this one: discard any swollen can, no exceptions.