Drink lots of water.
If you want some junk food, have some junk food, but instead of having a full bar of chocolate, have half and leave the rest until later, or instead of eating 2 packs of crisps, eat one, etc. Restricting yourself totally will only lead to you craving it more and going crazy when you get it lol
Try buying less junk food, the less you have the less you’re going to be tempted. If you’re not the one buying the snacks ask the person who is to buy less/put the snacks in a different place. If you want a snack, fruit (apples, bananas, oranges, a handful of berries or grapes, whatever you have), yogurts, popcorn, crackers etc are ‘healthier’ things to snack on x