Basically if someone didn't catch what you said they will say "please?" instead of saying "what?" or "could you say that again?" like a normal person. It seems to be more common with older people. I don't hear many young people saying it.
It seems like most people around here say pop, but I've always called it soda. I never got into that Cincinnati thing of saying "please?" instead of saying "what?" either. I always thought that sounded weird.
I don't think there's a Cincinnati accent although some people do have a touch of a southern accent given that Kentucky is on the other side of the river.