You can sell off the water dishes, make a pool of water for them, and put them in it. Sometimes they won't drink from pools until they've been 'baptized'. If there are water dishes, they will go for them rather than for the pool.
Another thing is that whenever you get the message "X is really thirsty!" the animal's action will automatically switch to 'Looking for something to drink' even if it was going to drink before.
Meerkats are also really social. Check their actions. If they have other basic needs to fulfill, let them. But if all they can think about is hanging out, you may have to quarantine them.