Back when I could get free food at work, they would get yellow cake with vanilla icing about once every other week. They see you get out of the car with a cake tray now, they start jumping the fence and mobing you! I'm down to 40 chickens now (from 65), so each one doesn't get that much, but they love it. They also love to sling colored icing everywhere. My poor little white cochin was blue, pink, and purple for a week! It had to happen when I didn't have a camera that worked too! Junk food in moderation should be fine, mine still get homecooked bread in the afternoons when I sit and make them come to me. They have to eat it out of my hands (or steal it from one who does) to get any though. You would be surprised at how much bribery does for you!