Junk food is a food item found in Fallout 3.
It can restore some of your Hit Points, but also gives you a small amount of Radiation. They are visually identical to Potato Crisps - the in-game box and the Pip-boy icon are the same.
They are more commonly found in Eat'o'tronic 3000s, in houses and other living spaces, but can also be found more scarcely in various buildings around the Capital Wasteland.
Even though it encourages people to "See the moon map offer on back!" the box's back side is an exact copy of the front side.