Mine are like b.hormada's, not picky. I give mine scrapes from my garden and the pepper tree that grows over the coop drops leaves for them. During the summer I give them frozen water melon to cool them down and keep them hydrated. Strawberries are a flock favorite, but a have a chicken obbsesed with kale. Meal worms gives my rhode island red the runs, so I cut them off of that. But they love this:
They are soft so I pinch them which turns them into powder and I scatter it around the coop for them to scratch for.