Scientists have found ancient water trapped in rock. It’s millions of years old and still drinkable.
But your plastic bottle is not ancient rock. It’s a modern convenience designed to be used now.
Think of bottled water like a loaf of bread. Bread lasts a week. Bottled water lasts two years. Both are fine, but neither tastes great after a decade in a hot truck.
What about that one bottle from 2018?
You know the one. It’s behind your spare tire. The label is peeling off.
Can Water Go Bad In A Thermos at Doreen Woods blog
If the seal is intact and the plastic hasn't melted, it’s probably safe. You won’t die.
But dare to drink it. Notice the plastic aftertaste. Notice how your mouth feels a little... weird. That’s the lesson.