Every summer, a half-finished case of Coke ends up forgotten in the garage, the basement, or the trunk of somebody’s car. By the time you find it, the date stamped on the cans is long gone. The good news is that cola is one of the more forgiving things you can leave sitting around. The real question is how it tastes, and whether the can in your hand is regular Coke or Diet Coke, since their sweeteners hold up differently.
Does Coke go bad?
The short answer: Not like perishable food, but it does lose quality over time. An unopened, undamaged can or bottle of Coke is acidic and carbonated, so bacteria have a hard time growing in it. What you’ll notice with age is flat fizz and a duller taste, and Diet Coke’s sweetness can fade as its aspartame breaks down, especially in heat. Coca-Cola defines its printed date as the last day of peak taste and quality, and USDA says dating on shelf-stable foods is about quality, not safety.
For a complete pantry storage reference, see our Food Storage Guide.
Does Coke Go Bad: At a Glance
Unopened regular Coke, pantry
Per USDA, a past-date product should still be safe if handled properly until spoilage is evident; fizz and flavor fade
Unopened Diet Coke or Coke Zero Sugar
Same safety picture, but both contain aspartame, which can fade faster in heat
Opened, refrigerated
Best fizz within a day or two; quality drops after that, and discard it if left out for a long time
Storage
Cool, away from temperature extremes; USDA says below 85°F is best for shelf-stable foods
Bulging, leaking, or rusted container
Discard without opening, whatever the date says
Caffeine (12 fl oz)
34 mg in Coca-Cola and Coke Zero Sugar, 46 mg in Diet Coke, per Coca-Cola
Key Takeaways
Phosphoric acid and carbonation make Coke a poor home for the bacteria that cause foodborne illness, so in a sealed, intact container age mostly shows up as a taste problem.
Coca-Cola says its “best if used by” date marks the last day of optimum taste and quality. USDA says dating on shelf-stable food is for quality, not safety.
Extremely old Coke is a different story: a University of Georgia food safety specialist said there is no research showing a 41-year-old bottle is safe to drink.
Diet Coke’s aspartame fades with time and heat. In an FDA review of manufacturer studies, 62 percent remained after eight weeks at 86°F. Less than half remained after nine weeks at 104°F, so a diet cola stored somewhere hot is more likely to taste off.
For shelf-stable food in general, USDA says below 85°F is best, and heat is the storage factor that matters most for Coke’s flavor.
Cans and glass hold fizz better than plastic bottles, and an opened bottle with a tight cap beats an opened can.
Why Coke Is So Hard to Spoil
The tart bite in cola comes mostly from phosphoric acid, which does more than flavor the drink. A chemistry FAQ from Frostburg State University explains that phosphoric acid slows the growth of molds and bacteria that would ot
