Have a look at these, they will be much easier to keep neutral (and drink from) than a standard water bottle. Also. wont break the bank:I've thought about it. I'm probably going to put a waterbottle on a boltsnap for my next scuba vacation.
https://www.amazon.com/Assorted-Reusable-Collapsible-Foldable-Bottles/dp/B01APVV840