I bought a six pack of diet caffienne free pepsi in St Marten and carryed right on board. We purchased( through room service ) a bottle of rum( 22$) and made drinks in our cabin , and as I am affected by caffiene , I enjoyed a drink or two before or after dinner without worry. I never took my drinks( the ones we made) out of the cabin( I ordered a chocolate banana every day by the pool, yum) but hubby did take a rum and coke out to the pool area a few times. He just used the plastic tumbler the steward had provived us with.
We aren't actually cheap, we just like what we like, we do make bar purchases, and we did order our rum through the ship.. I also love diet Dr Pepper, and that is impossible to find almost anywhere except in cans.