Iced tea
A lot of Doctors want you to start out with Decaf because they are concerned about the diuretic effect of caffeine. I've seen a lot of people say that if you are already used to regular tea it won't really be a problem.
I think whatever helps you get liquids in is fine. If your OK with decaf I would use that until you have an easier time getting your liquids in. (For me that was a couple of months after surgery).