Hm.. that's a hard one. Have you tried feeding the rabbit banana? Maybe you could try feeding it some banana and eventually add a little bit of normal rabbit food in it. Add a little more normal food to the bowl each time and a little less banana.
If that doesn't work maybe try feeding it dry instant oatmeal. I did that with my rabbit. Like with the banana, add some normal food to the oats and each time add a little more normal food and a little less oats. Try to trick it into eating.
As for the water part, I'm not quite sure with that one. Defiantly leave a normal water bottle in there for bunny, see if it catches on eventually, but if it doesn't, that's when I would take it to the vet.
Sounds like it's still pretty young too, maybe it just hasn't quite caught on yet