Let’s be real. Drinking water that’s been open for a week won’t kill you. Unless you see visible mold floating in it (which is rare but possible in a super dirty bottle), you’ll probably be fine. You might get a slightly upset stomach if the bacteria load is high, but you’re not facing a trip to the ER.
The bigger risk is the taste and the ick factor. If it smells funky, tastes like plastic, or has been sitting on your nightstand for two weeks, just dump it. Your thirst isn’t worth the mental anguish of drinking it. I promise. Your brain will thank you.
So, to answer the original question: Two to three days if you drank from it. Four to five days if you poured it clean and kept it cold. After that? It’s not fresh, but it’s also not toxic. Use your nose and your gut—literally.
Now go drink some water. But maybe grab a new bottle first, yeah? I’ll be over here hunting for that road trip culprit under my seat. Spoiler: I didn’t drink it.
