I found baby bunnies and I took them in because they were drounding I just fed them lettuce and they eat off of carrots but they wouldnt really eat much because they were a couple days old so I got a bottle for bunnies and the stuff to put in it I'm not sure what it's called but I gave them that
google it! well... based on an adults diet i would say lettuce, cabbage, celery leaves, spinach and other green leafy vegetables. small carrot pieces is a treat and hay is a staple food they will need to grind their rapidly growing incisors.
At most pet places like Petco they got a milk that's specially made for baby kittens and other baby animals. You will need to feed this with a dropper which they also have. Assuming your talking about baby rabbits that can't eat hard food.