If you don't have junk food in the house it's a lot harder to eat junk food. Good eating starts at the grocery store. I eat a lot of fruit (frozen strawberries are a big one) and popcorn (with can't believe it's not butter spray) and sugar-free chocolate pudding when I'm trying to cut weight, lots of volume and flavor but not that much calories per unit of volume, and that works out okay. (running 40 miles/week also keeps the weight off, but it's definitely not for everyone)
On the other hand, diet isn't top priority at 20 days and if you want to eat like a college student home on break that's probably alright.