It's fun to introduce the chickens to new foods. Kind of reminds me of what it was like to give my kids their first taste of a new food. Like kids, they play with it for a while, roll it in the backs of their mouths, and then proclaim it good or terrible. Actually, with chickens, even if they don't like it, they'll still peck at it on and off throughout the day. Heck, these birds eat DIRT, so what else won't they try?
I've read that chickens like yogurt, which makes no common sense. In the natural world, when would a bird ever come across a blob of yogurt? And they're birds, for goodness sake, not milk-fed mammals. Still, there you have it: One little bowl of yogurt, and they're immediately dipping their beaks in it and getting it down somehow. (Is there a tongue in there? Must be...)
They also like certain weeds, namely chickweed (thus the name) and they're fine with dandelion leaves and anything in the garden that's bolted. They especially like buckwheat sprouts, too, and they'll even eat grass.