Here's what I did for food this summer while bike/backpacking in Oregon.
No heavy cookware or fires required. Everything can be purchased in the bulk section of a good food store, ideally your local food co-op if you have one. Everything lasts a long time so you can keep your leftovers for next trip. This is healthier, less expensive, and less polluting than buying typical backpacking food. It's basically the same food that goes into protein and granola bars, but unprocessed, without the chemicals and stuff. It’s very tasty too, and with a variety of seasonings, you can get a wide variety of delicious combinations.
The basic idea is to eat rolled grains, soaked, with nuts/seeds and seasonings added in. I'll tell you what I buy, roughly how much, and how to carry/use it.
. . .
What to buy?
rolled barley (and/or rye, spelt, wheat)
lentils (many possible varieties)
peanuts / peanut butter
etc (whatever you like, but don’t support the cashew industry)
Greens: (for nutrients)
raisins, or whatever you like! raisins are usually the cheapest, I also love dates, craisins, dried blueberries, and dried currants.
whatever else you want!
I like pepper, nutritional yeast, curry powder, cinnamon. But there are plenty of options -- use what you like.
bowl and spoon (I use one of those tall plastic yogurt containers as a bowl)
durable container with screw-on cover for soaking lentils (soak for 8 hours, e.g. overnight)
How to prepare?
Put rolled oats or barley in your bowl and add water. Let sit for 5 minutes. Then add in all the other ingredients, whichever combo you like, stir a couple times with the spoon, and eat.
How much to bring?
I’m 6’4”, ~190lb and a big eater. For 10 days, I had roughly:
8lbs rolled grains (~1800kcal, 60g protein / lb) ($0.50-$1.50/lb)
1lb dry lentils (~1600kcal, 120g protein / lb) ($1/lb)
4lbs nuts/seeds (~2800kcal, 90g protein / lb) ($2-$15/lb)
1lb dried fruit (~1500kcal, 15g protein / lb) ($3-$10/lb)
for a total of roughly 3000 calories and 100g protein per day, costing about $50 for the food, plus I spent about $20 more on greens and seasonings. I buy organic — if you don’t, it’ll be even cheaper. I am lucky to be on the west coast of the USA where these foods are relatively inexpensive, too. Other parts of the world it may be pricier, but still probably cheaper than processed foods. I don't eat this much when I'm not getting intense exercise every day.
Dried greens don’t really count toward calories — basically bring as much as you can afford, the nutrients will make you feel good.
How to carry?
Use reusable plastic bags or containers for everything. You can use these same bags for buying in bulk and carrying with you. Use a little gorilla tape to patch holes in the bags. Like any backpacking food, you should either hang it from a tree in some kind of larger bag, or put it in a bear canister.
. . .
My favorite combos:
Sweet: soaked oats, cinnamon, walnuts, chia seeds, dried fruit
If you’re in a place where plants grow, learn to forage greens, herbs, and berries. Don’t count these for calories, but they’re great nutritionally. In california and oregon, miner’s lettuce is all over, for example.
If you let your lentils soak long enough they’ll sprout which is OK! They can soak for days and still be OK to eat. They'll be slightly crunchy but perfectly palatable after 8 hours soaking.
No need to wash your bowl (although you are welcome to). Just eat it mostly clean, and let it dry in the sun. I went a month without washing it with soap, only rinsing it with water occasionally.
I like to bring a little coconut oil. Rinsing your mouth with coconut oil is a good idea in addition to brushing. I just swallow the oil after rinsing, so it’s not wasted.
I love walnut flavor infused in the oats, so I chew the walnuts a little and then spit them into the bowl, when I begin soaking the oats. You could also crush the walnuts, but I find that more difficult to do.
Sesame seeds are great and cheap, but they're hard to chew if you mix them with other food -- you'll end up swallowing them whole, and I believe some of them won't be digested. So I eat spoonfuls of just sesame seeds, separately. If you can grind them before the trip, then they're fine to mix in.
Flax seeds are also great and cheap, but you need to either grind them before the trip, or roast them and eat them separately just like the sesame seeds. Eating raw whole flaxseed is difficult, and won't work at all mixed with other things.
Bring enough salt! With no processed foods, all the salt you get will be the salt you bring, and the little sodium that's found in these foods. I'd guess you want at least 2-3g of sodium each day -- but I'm not a nutritionist.