I buy the cheap big bags of WalMart's brand of rice crispies for my hens. It's a pretty good treat! They love it! When they see me with that big yellow bag, they come running!
Im sure they wouldnt mind stale rice crispies either? I have a bag bag that I was gonna use for a recipe, but never got around to it. Im pretty sure they arent any good now. Do chickens care if its stale?