I switched to a bowl (coop cup) because one of my pigs liked to chew on the spout of water bottles emptying them everywhere in the process including all over himself. The superpet(?) glass water bottles with little floating ducks/carrots in are pretty good though, I have one for my rats after contending with loads of leaky plastic ones and because they started chewing them. If you do get a glass one check the screw thread on the spout/top allows you to screw the top on so the spout points in the right direction, the bottles have a flattened side so if you want it on the outside of the cage then the spout should point towards the flat side when the top is screwed on (obviously we realised this after we bought it!).