My profile piggy has bladder stone problems, and he's a terrible drinker.
Everyone has said he needs to drink more, but it's quite time consuming syringing him water.
The CCT recommended what we call his "juice". It's 100% fresh orange juice (Innocent or similar) really really really diluted in water. He has one of the little mouse bottles full of water with maybe 5ml of orange in it. He'll drink about 20ml of that, sometimes 45ml or more.
The only problem is it needs changing twice a day as it's fresh orange and so goes off really quickly.
Saying that though, if a pig drinks water without a problem, then that's all they need. They're not really built for drinking anything else.