I saw some instructions for making your own MREs, but they just shoved junk food into a Ziploc bag.
MREs are at least made from food, even if it isn't tasty food, or if it doesn't still resemble it.
Exhibit A: Wheat Snack Bread:
It isn't wheat, it isn't a snack, and it isn't bread, but as long as it is unwrapped, you can sit or step on it without damaging it, and it will last until peace breaks out.
You can't do that with wonder bread.
It seems weird to pack dry food when you need to pack water to compensate, but it lasts longer that way.
They have soups and stews, but I have never seen ready-to-eat pouches in a grocery store, just camping suppliers.