Limit treats and never feed your rabbit people food. Rabbits have very sensitive digestive systems that are designed to ferment hay and grass to get the nutrients out of it. Adding other foods to that system can easily upset it.
Avoid people food, even if you think it would be healthy for a rabbit. Why risk it.
We once thought giving her a few pieces of air popped popcorn would be fine. Unfortunately, the starch in the corn doesn’t agree with rabbit’s digestive systems and gave her gas. The gas caused bloating and stopped the flow of the correct food through her system. When the flow stops the bacteria that help break down the grass and hay can get out of control and lead to death.
Fortunately we found out the problem in time and were able to administer Pediatric Simethicone as per:http://www.rabbit.org/chapters/se-pennsylvania/GIStasis.htm and with a fair amount of gentle stomach massaging she was better (trust me, you’ll know when they get rid of the gas).
Knowing that our thinking her eating popcorn was cute almost did her in was a real wake-up call. Don't ket your rabbit decide what they eat; remember if it were up to them they'd eat electrical cords, rubber bands and erasers.
Just because it says it is for rabbits on the label and the pet store sells it doesn’t mean it is really good for them. Treats should be given only rarely. If your rabbit is like Spot then it will act like it is starving and needs the treat to survive but if you give them more than a couple a day you are doing them a disservice and may be shortening their life. Avoid the bright, colorful fancy treats in the pet store. Stick to small amounts of treats and go with the ones that are a natural green that smell like hay. We've had really good luck with Oxbow Products.
The best treat you can give your rabbit is plenty of fresh Timothy Hay (Alfalfa is okay for young rabbits), plenty of fresh clean water and good quality pellets (timothy hay based ones for older rabbits and ones with alfalfa for younger).
Access to fresh clean water is very important. Something to keep in mind is if, due to some type of emergency, you couldn't get home for a day or so would your bunny have enough water to make it?
A small handful of fresh veggies a couple times a day are also great and needed for good health. Don't let the giant carrot in the picture fool you, the actual carrot is full of sugar and not really good for bunnies. She got to nibble on the top for a bit, pose for the picture, and that was it.
Here's a good list of suggest veggies :http://www.rabbit.org/care/veggies.htm Spot wouldn't chew the leafy stuff enough and tended to choke (bunnys have no gag reflex) on it so we have to cut it up small and scatter it around her cage. Rabbits love rose petals, just make sure the roses aren't sprayed with any chemicals. No worries though, this: http://www.rosemagazine.com/articles02/pages/mildew.asp works far better than any harsh chemical sprays on roses.
Moderation is the key to any treats for rabbits just like for everyone. Watch your rabbits weight and their activity level. Remember to keep them exercised.
Treat ideas: Save a Fluff