In other words pretend you’re one an overnight field trip in high school. 
Shampoo/conditioner bottles work for any kind of liquor, but make sure you thoroughly rinse them out first.
I’ve put booze in mouthwash bottles, and also packed it in my luggage with no problems.
Also, they’ll x-ray bags coming back from shore, but pints that you can carry on you usually aren’t detected when walking through the metal detectors. Smuggled on a couple of bottles of nice Bahamian coconut rum that way.
If you really want to sneak liquor on board, just put it in some sport bottles, I usually take a bottle of vodka and a bottle of rum in, with a drink card you’re all set. And if you get to play games, the winners usualy get a bottle of champaign that you can drink anytime, we had ours chilled for dinner. Oh and the last cruise I won 4 bottles cause I’m greedy. And take a good book, there are some real slack times on ships with no activities worth participating in.