Veggies and fruits are excellent chicken food, provided they are not infested or moldy. IME, the favourites are:
But just about anything goes. My chickens won't touch citrus fruits, however. Lots of greens like grass and celery are great for their health, so make sure they get plenty especially if they are confined to a run like mine are. They seem to love moist and watery foods like watermelon, but too much obviously causes loose bowel (so go easy on melons). A little minced garlic is good for their health too. I hang the fruit and veggies in one of those hanging plant baskets to keep it clean and out of the dirt.
Hope this helps.