I have seen people carrry on a case or two of sodas, especially if they are brands that are not typically sold on board. Coke Zero, is my soda of choice and most cruise lines do not carry it. as long as the box does not apper to have been tampered with, aka opened and resealed with say a case of beer instead of cokes...it should be okay. But again check with your cruise line first, the worst thing they will do is hold up your luggage in the 'naughty' room and confiscate the beverages until the end of your trip. Just like travel irons and such.