Hands down, Andrew Skurkas refried beans and rice. It’s dehydrated refried beans, minute rice, taco seasoning, cheese, and Fritos.
Excellent cal/Oz ratio, great balance of macro nutrients, easy to prepare, simple ingredients, and readily available (online lol).
Idea of an explanation and recipe:
https://m.youtube.com/watch?v=XQp81n8uzzE