A BurgerBag project
This project is a solution for everyone who share an apartment or a flat with strangers just like in case of many students who are studying abroad and living with foreign housemates.
Imagine when your pack of bacon or your bag of Cannoli was opened without your permission. You will get upset and write down your name on the plastic bag or a fruit package which it may hurts one's feelings in your small group or the bad case is everybody will look at you like a narrow-minded person. So I do think it's not OK enough for this piece of cake thing.
This is the best solution for you who got a trouble!. Just go to Sainsbury's, buy pizza, take it into this bag and go home. So the dudes will never touch it and they will think that this doggy bag in the refrigerator might comes from a famous restaurant or an popular advertising campaign. . . of course, they will never know your name.