Sparkling water is just carbonated water. That means carbon dioxide gas is dissolved into it under pressure. When you open the bottle, that gas starts escaping into the open air (a.k.a. your kitchen).
Once the seal is broken, the clock starts ticking on the fizz. After a day or two, it starts losing its sparkle. After a week? You’re basically drinking defeated water—water that has given up on life.
But here’s the weird part: even unopened bottles can lose some fizz over many months. The plastic or metal isn’t a perfect fortress, and tiny little gas molecules eventually sneak out. It’s like the water is on a very slow, stealthy escape mission.
Does It Ever Go “Bad-Bad”?
Unless you leave it open for a week next to your garbage bin, no. Sparkling water isn’t sugary, so it doesn’t ferment or attract bugs. It won’t grow fuzzy fur or turn into a science fair project.
Water: Sparkling or Still? What the Science Says | WellnessPulse
The only real enemy here is stale air and weird smells. If you leave an open bottle in the fridge, it can absorb the smell of last week’s leftover fish. Then you’re drinking “essence of old salmon” sparkling water. Do not recommend.
