It's amazing how well the protein/carb/fat profile of a Snickers bar matches that of most "energy" bars. Tastes better, too, but you need to buy them from a convenience store/gas station in the summer or they'll melt.
If I need salt, I look for a V8 or Fritos, and some stores have French fries (and you can add even more salt!). On one overnight brevet, a fellow rider got me to try some Campbell's chicken noodle soup in a bowl; microwave that, and I had enough salt to go another 6 hours plus carbs from the noodles.
Some gas stations have a Subway attached, or a food section with prepared hamburgers (yuck) or fried chicken (eat the chicken, skip the breading, please).
Worst choice: refrigerated burritos.
Best: one little place in Virginia (Catawba, maybe) had a grill and had just cooked a bunch of fresh hamburgers.
I could go on, but it's lunchtime and I'm hungry now.