I think the third option should be Sodiepop. I only knew two people who called it that, and they both said Sodiepop instead of sodapop. Even Cotton on King of the Hill said Sodie pop.
Soda! "Would you like SOME soda?"
Pop! "Would you like A pop?"
Sodapop! "I'm old!"
Coke! "I'm from the South and we call everything Coke!"