On Princess and HA , I've ordered thru my Travel Agent for Rum, Coke and Ginger and once onboard after a few days ordered more via Room Service.
You can get a package of mix and most times a pack of coke of 6 comes with price only of five.
I have the room steward move out of the fridge the cans the ship placed prior explaining why and then stock mine.
Normally a card will be in your room asking you to call for delivery to your room when you first come onboard.
It is nice to be in your cabin on the balcony having a wee dram.
and as someone said, not having a wet suitcase.