While I'm not 100% positive, I'd doubt they do. NCL serves coke products -- primarily coke, diet coke (w/ caffeine) and sprite. There may be a couple of other choices, but that's all I remember.
We've taken our own soda on board -- I drink Diet Dr. Pepper, my son prefers diet Pepsi, and my husband like Fresca. We've never had any problem taking a 12 pack of each on the ship, so to be safe, I'd just take your own.