The 'usual' canned soda selection includes:
Coke
Diet Coke
Sprite
Root Beer
Orange Soda
Tonic Water
Club Soda
Ginger Ale
Also included are: Red Bull, Perrier, San Pelegrino and Mocktails.
That being said, there are no guarantees all cans are always available on all ships. There are random reports of 'other' varieties showing up. I think this usually happens in Europe where some substitutions might be made. (You can find entire threads on Coke Zero, which seems to randomly show up mostly on European cruises.)