oh okay well we bought it and on the gallon has like 2 expiration dates so idk
If you leave it in the heat and drink it it's terrible for you. It heats up the plastic and releases chemicals that are harmful to you.
One time use shouldn't effect the baby.
The weird taste may have been if it was left out in heat. If left in the heat for to long releases some chemicals into the water. Leave a horrible taste.
Yes water has an expiraton date on the gallon or case of water. Check for it. If you open it and left in in the fridge for that long it probably went bad if it's not properly refrigerated or if it doesn't have a cap in it.