Hi hikenhunt,
I usually eat a pretty clean diet, low sugar, low fat, stay away from processed food/fast food. But when it comes to the outdoors, I throw out any idea of eating right and pack on the calories.
I always seem to go back to the PBJ sandwiches, cheap, easy to prepare and pack relatively ok, by that I mean they squish into any area of the pack or pocket.
I've also used mil surplus MREs, they are designed to be consumed during high exertion, physical activities. They do have a lot of fat though, which I assume is where a lot of the energy in the meals comes from. .
Also, don't forget the electrolytes. Very important if you are sweating a lot. Salty snacks or supplements. Either one.
Last but most important is water and plenty of it.
I stay away from the power bars and energy snacks you find in all the stores. They are usually laden with processed sugars or sugar substitutes and I do not rely on them for sustaining energy. But, I do have one in my pack. If I'm really exhausted and there's one more climb to make it out, I'll down that with lots of water. Just to give a little burst to the finish line.
I'm not saying this is the ultimate answer, just what I find works for me.
Merry Christmas, hope the holidays are being good to you,
Jim