Most of us grew up being told not eat between meals. The explanation: "You'll ruin your appetite." True. But isn't that exactly the point of eating, to ruin one's appetite?
Just make sure that you ruin your appetite with nutrient-dense snacks.
I've found that one of the best practices when on the road is to never get too hungry. Of course, bad decisions are made when desperation sets in. And in a world of low quality, highly available fast food, it's a challenge not to cave in when you add hunger to the mix. Not something any of us need.
Surprisingly, most North American cities I've visited offer decent accessibility to whole food. Even some convenience stores, many of them open 24 hours, have reasonable options for grazers. Fruit, vegetables, nuts, and seeds, etc. Some will offer bananas and apples. Nuts and seeds are even more common. Choose the ones with nothing added. Ingredients should simply be nuts or seeds. And a bit of salt is fine, but avoid ones with added flavors and modified oils. If you're desperate (you shouldn't be, since I'll have your homemade bars with you), then some commercial granola bars are not a bad option. Just make sure they don't have hydrogenated oil listed on the ingredients. Increasingly, fast food restaurants also offer green salads. That's good. Just make sure to get the dressing on the side, or avoid it all together. Most fast food dressings are laden with empty calories, derived from low-quality oils.