Instead of having customers donate a dollar and giving them a coupon book "worth" $30, why doesn't KFC just donate those $30 themselves (or even half)?
Edit: I've been corrected in the comments. Happy to be wrong about this so thanks to the correctors.
Charitable donations can be written off on the businesses taxes, so by having customers pay for the donations it means the company gets to double dip. They write it off and the customer reimburses them for it.
Moral of the story: don't donate to corporations. Give it directly to a charity.