Bunnies have different tastes and what one likes for treats differ from another. Some like bread, apple, carrot, potato peelings, berries, banana, comfrey or parsley. Remember, all small portions. Never give lettuce as it has too much water and can give them diarrhea. Never give cabbage, it could tie up their digestive tract. Don't give them broccoli, too gassy, again a stomach problem maker.
Gemstone and her sister Blue Sapphire tend to take their small piece of bread and run circles around their cage with their "prize" held high in the air, noses pointed skyward. They run round and round like someone is likely to snatch it away any instant. This either stems from when they were babies and keeping littermates from snatching their treats away. Or could have come later when they had babies of their own that would steal a treat if put immediately on the cage floor. Eventually they tick down like a bad wristwatch and sit still to eat their prized treat.
We usually feed pieces of whole wheat bread but one time I'd brought home some white bread. I don't know just how colorblind a bunny may be but one doe definitely knew the difference. She normally loved her whole wheat bread. But the second I set the small piece of white bread down, she startled and ran away from it. No coaxing changed her mind and she kept her distance or ran away when I tried to put it near her. She was scared of the white bread. Next time she was offered whole wheat and woofed it down. Silly doe.
Like the 5 minute treat gone rule, if they show no interest in it within 5 minutes, remove it, they don't want it.