Below, you will find a list of healthy snacks for the road (at the bottom is where I listed the not-so-healthy ones). I hope this helps in some way.

Cleaned and sliced raw vegetables; grape or cherry tomatoes
Apples, oranges, bananas, grapes
Snack size dried fruit (such as raisins)
String cheese
Yogurts in a tube
Pretzels
Roasted soy nuts
Baked, flavored rice or popcorn cakes
Sugar free jello cups / fat-free pudding cups (with plastic spoons)
Reduced fat cookies/crackers
Fruit juice boxes; mini cans of low-sodium V8 juice
Whole wheat bagels with light cream cheese (bring a plastic knife; slice bagels before leaving)
Sandwiches of your choice
Trail mix
Dry cereal
Brownies or homemade cookie bars (they hold up pretty well during a road trip)
Pepperoni slices (my son just eats them straight out of the back sometimes)