I was surprised how tasty Ramen noodle soup was for breakfast, I did that every morning for a short trip. Soup was $0.25 not counting cost of stove fuel to heat the water and cleanup water. Extremely fast and very light weight to carry. Some instant coffee or a few tea bags adds a bit more cost.

Knorr makes several rice dishes, when I am traveling alone I find that half of a rice mix packet with one can of soup or chili can be quite filling.

I usually start a trip with about 6 to 8 hard boiled eggs in my pack that I fixed up at home. How long they last in the pack varies with the weather, I avoid touring in hot weather so for me they last several days. They are a handy thing to have when you are craving some more food in the evening. But during the day while riding, you would want something with carbohydrates instead of an egg. Eggs after a day long ride can be a good source of protein to aid muscle recovery.

I will start a trip with a couple boxes of granola bars in my pack for extra calories during the day while riding.

For travel I am not a big peanut butter and jelly fan, but a gal I used to work with ate that a lot on her camping and kayak trips.

For a week long trip, if you do not keep up on all your calories, it is not a big deal. A multi-week trip is where it becomes more important to keep up on calories. When I did the GAP/C&O trail, I got home about 3 pounds lighter for a week long trip with no ill effects. I think that was caloric deficit, not salt depletion because my weight did not rebound within a week after I got home.