When we're driving, I prefer to eat just a grilled chicken sandwich from DQ or Chick-fil-a, fills me right up. Of course that's still around $4-5. We only drink water or iced tea that we carry with us in reusable bottles, saves us a couple bucks. Man, do they charge for drinks.
We both try to avoid fries. But Culver's up here has good crinkle fries and she loves them. Don't even put salt on them, they're already salty.
Fast food just isn't good for us anymore. Maybe ok for you, that's your choice. When I sold my minivan, we found a couple of McD's fries from 3 years prior. They looked and smelled the same as new. Just seemed ... wrong. Stopped eating there. :P