We're not drinkers any more for medical reasons, but we need our Diet Pepsi & other diet drinks. We don't try to carry them on the plane, but we've always been able to buy them before we've boarded the ship or in the different ports. When we were drinking we were able to bring the brands of "local" beer that we couldn't buy on the ship on board.
What ever you do don't pack liquire in your checked bags. We had bottel of rum break in the suite case and everything had to be sent to the cleaners or laundry at the strart of the cruise.