I was diagnosed with Celiac Sprue in 2016 a few months prior to leaving the military. Nothing like being told in your late twenties "oh, by the way, you can no longer have bread, beer, or general happiness."
After four years of dealing with this illness, I have learned to cope but I still miss donuts...
Now, preparing for my through-hike of the Appalachian Trail, I did my research and listened to everyone I could about what to take on the trail, as far as food. The biggest issue is that there is not a ton of cost effective ways to get the calories you need on trail while not being able to eat wheat or soy (yes, soy too).
So here is what I did eat:
Certain Clif Bars
Oatmeal (not quakers since they are not GF for some reason)
*GF Tortillas (Corn or Spinach) with Peanut Butter and Honey
Cap'n Crunch or Lucky Charms (because I'm an adult)
*GF Tortillas with Pepperoni, Cheese Sticks, Spinach, Special Sauce (or Mustard) and Fritos (yes Fritos)
Cheese (usually Gouda, White Cheddar, or Horseradish)
Trail Mix (be careful with these though, they are not all GF and any that have M&Ms have soy)
and Anything that I would eat for dinner could also be part of lunch (If you are hungry, you eat, and your body tells you what to eat)
Dinner (aka Feast Nights)
Mashed Potatoes usually Instant
Olive Oil (sometimes)
Fruit Leather, Gummies, Roll-ups, Gushers, or just plain ol' Fruit
Tuna (or Salmon)