Lowkey that’s not a bad idea but then everyone would likely get rich asf and the amount of water bottle you own would indicate how rich u r

The original concept of the bottle caps being a currency was that clean water was a scarce resource and more valuable that virtually anything else. But carrying around a shitload of clean water is a pain, so cartels formed banks of clean water in different settlements and since bottle caps were also finite and difficult to reproduce, easy to verify, so the banks would issue them as a sort of cashiers check, you drop off clean water at one bank, get bottle caps and can redeem those at any of the cartels other banks for clean water. From there the caps became a bartering tool and then a currency, since trading an item for some bottle caps was as good as trading it for fresh drinking water.