Why does bottled water have an expiration and should you care?
The answer is yes and no.
One of the reasons water has an expiration date is
because by law any consumable product should be labeled with it just like your butter, bread and
salad mixes. In the case of bottled water, yes its ridiculous to think that water could actually expire, it does not. However, the plastic the bottle it's made of does expire and it has chemicals in it. Chemicals that can leak into the water, disturbing its taste.
What you can do instead is pour the water into something else like a glass cup or reusable bottle, when you notice it's closer to its date of expiration.