In many places, including parts of the US, bottled water must have a “best by” date. It’s a labeling law.
Think of it as a quality promise, not a safety warning. The water won’t kill you. It will just taste like a Tupperware container left in the attic.
Fun fact: the FDA doesn’t actually require expiration dates on bottled water. But manufacturers add them anyway. Why? To cover their butts.
Does Bottled Water Really Expire? - YouTube
The gross stuff that can happen
If you leave a bottle open, bacteria move in. Your mouth germs, airborne dust, maybe a stray ant. That’s not expiration—that’s a microbial party.
Unopened bottles stay cleaner. But if a bottle gets scratched or dented? Tiny cracks can let in nasties.
And don’t even think about sharing a bottle after a workout. That backwash is a biohazard time bomb.
Here’s a wild one: algae. Leave a bottle in direct sunlight for months, and green stuff can grow inside. You’ll see it. You’ll smell it. You’ll never look at water the same way.
