On RC, We took 4 cases of Pop & 3 different liquors on board in suitcases (there were 3 of us, 1 rum, 1 vodka & 1 gin). One duffle bag was the cases of pop only. Had no problem at all. Cabin steward kept 2 buckets of ice in our room at all times. We even had the waiter get us limes to take back to our cabin. On RC I took the liquor in plastic flasks, but I also went on Carnival & just took the bottles (securely packed for no leaks, of course!). We kept these bottles out on the desk and didn't have any problem. We ran into several couples on the Carnival cruise who had brought in several cases of beer -- I'm not sure how they kept it cold. But we had no problem on either cruise line.
We just pack a bottle of liquor in each roll-on carry-on tucked between our change of clothes and personal vanity supplies! As mentioned,just ask your steward for limes, juices; OJ, Cranberry and purchase other mixers at port if necessary; Tonic Water was a little difficult to find! Sometimes I also bring Sparkling Water too as I don't drink much soda. I don't openly consume or mix a drink on deck, but do put it in my personal water bottle for enjoyment by the pool. If you enjoy beer or soda, just bring a can coozie with you. No scams no tricks.