There are several options for sneaking alcohol onto a cruise, all determined by how much you want to spend and how creative you want to get.
You can get a 12-piece camo flask set
on Amazon for $20.00 which will hold enough alcohol for a 7-day cruise at moderate drinking. You will need to pack this inside another bag which is inside your check-in luggage (do not carry on)
They also sell disguised shampoo and condition bottles called Smuggs Jugs
which you can use to store booze as well,
is another option and they claim their product is non-leaky.
Finally, the most popular of brands seems to be Rum Runners
and here you can watch this video
which shows you how to properly pack your carry-on so that your cruise booze do not get confiscated.
As for drugs, it's not recommended that you try to bring them on-board. If you want to be daring though, vacuum seal the items and tape it to your inner boxer shorts. Most dogs that are at the ports are sniffing for explosives and not for drugs, especially when you are leaving. I would not recommend trying to bring anything back into the states and if your lucky enough to get away with this, flush any remaining before you disembark. You also do not want to end up in prison in a foreign country, as that will ruin your bachelor party.