Planning is key to not making poor choices when you are out and about. I always pack a yummy post weight loss surgery friendly snack in my purse so that when hunger hits I don't grab for crap.
Here's one of my current favorites...
Shelly's Emergency Stash Trail Mix
Gerber Fruit Puffs (Banana, Strawberry Apple, and Sweet Potato)
Kay's Protein Cereal
Special K Cereal
Just the Cheese Crunchy Cheese (Wisconsin Cheddar flavor)
Dried Unsweetened Cranberries
Mix 2 Tablespoons of each of the above together in a bowl.
Stir to combine. Fill 4 or more snack sized Ziploc bags.