Actually, if you just HAVE to bring some liquor onboard, all these "ruses" with transferring booze into all these odd containers is totally unnecessary!!
Pack it in your suitcases, and hand the bags to the porters, and they'll arrive in your cabin safe and sound.
The cruise line's know this goes on, and if they really wanted to put to a total stop to it, they'd simply insist the cabin stewards report any bottles seen in cabins..... so you really don't have to fool anyone!!!
I (and the cruise lines.. from their actions) believe there's nothing wrong wtih drinking your own alcohol in your cabin. BUT.. on land you wouldn't walk into a bar, or a lounge with drinks you mixed in your car. DON'T do it on a ship either. Enjoy the booze in your cabin, but if you want to enjoy drinking in the ship's public areas, bars, disco etc, pay the price!!!
The price isn't different than most bars and lounges on land.