Two of my pigs, Chompsky & Oppenheimer (really, who else?
) played with one of their water bottles constantly. I would fill it up in the morning and by the next day it was completely empty. They are the 32 oz. bottles. The other was completely full, untouched. I don't know why because to my human eyes the bottles appeared identical. So I left the bottle they preferred to play with empty for several days so their only source of water was the bottle they didn't play with. After a couple days they realized there was no water, therefore (in my opinion anyway) no fun to be had, and stopped messing with the bottle altogether. Now I can put both of the water bottles in and for the most part they leave the one bottle alone and only use it for its intended purpose.
I don't know why it worked, but maybe it's worth a try if you have another water bottle?