"Hey buddy, can you do me a favour?"
"What do you need?"
"I haven't eaten in like four days, and I'm a couple bucks short of getting a large pizza. Can you help me out?"
"I don't have any cash, but here, take this"
(reach into bag and pull out an apple fritter)
"Oh." (pause) "Thanks man, but I can't - I'm allergic to bread products."