At first I wasn't sure if you were serious or not! You can't (or aren't supposed to) take food off the ship with you, I've seen people do it though.
I haven't been on a ship yet that didn't have excellent crescents, chocolate so going off to bring food back on just doesn't seem logical.
I would not take something from my cabin and walk around with it. You don't see people walking around with bottles of beer in their hands.