Oh oh - pick me!!!!! We travel a great deal across a span of land with practically no place to stop.
I am not a fan of rice cakes because they make a lot of crumbs and toddlers can choke on them easily.
I take a bag of baby carrots and steam them so they are super soft. If dc is a choker you might want to also cut them in half lengthwise. They are still "finger food" but soft enough to chew easily.
Tortilla nut butter "crackers". I use whole wheat tortillas, spread nut butter on, put another torilla on top, and cut into wedges. More durable (and heat resistant) than bread, less crumbly than crackers, and a high protien source. I have also used refried beans as filler. Just go easy on whatever filler you use so it is not dripping out the sides.
Bananas are always a safe bet.
Sippy cup smoothy slush. Make very-well-pureed smoothies out of whatever you like (I use almond milk and fresh fruit), pour into sippy cups, and freeze. Halfway through the trip, you have a nicely melted but still cold "protien shake". Wrap these in towels to keep the condensation from soaking everything in the area. If you use a fruit with small seeds or a lot of fiber, try a sport bottle instead of sippy cup.
Dried papaya strips. Littler dried fruit tends to end up all over the place....it is hard to eat little things while sitting reclined in a carseat.
Fantastic Foods makes a couple of cup-a-soup like things. I stash a few in the car in case we end up at a fast food restaurant and nothing is appropriate for little kids. We will often stop at a ff rest to use the bathroom, get some coffee, and change dd. In that few minute break, I ask for hot water from the counter and make a quick soup (usually black bean or split pea). We do this primarily in the winter when there is too much snow for outdoor diaper change breaks.
And lastly, I always keep a few toddler size jars of organic baby food. Usually fruit or cereal/fruit mix. Dd never has these at home but sometimes it is a real treat for one of us to sit back with her and spoon feed her the jar like when she was a baby. she gets a kick out of it. And really anything that will buy some time is worth it IMO.