Even if you limit the consideration to foods that can be eaten as-is with zero preparation or tools, grocery stores still BTFO of fast food. Anybody saying that fast food is cheap is deranged. You want fried chicken and you don't have a kitchen? The grocery store will sell you 2x as much for the same price as a KFC. If you want a sandwich, you can make a dozen for the same price as one from a sandwich shop. If you can stomach the thought of eating something green, the produce aisle is cheap as dirt. It's an internet meme to say that some people can't afford fresh produce. Absolute horse shit. I can buy a bag of carrots with the change I find on the ground walking to the store. Produce is the cheapest food there is.
If you think all of that is too boring to tolerate, then scrounge up a can opener and the possibilities explode.
If you think all of that is too boring to tolerate, then scrounge up a can opener and the possibilities explode.