Chop one onion, one carrot, add fat, nasty meat bits or fish heads, and whatever else is going to rot in the fridge. 3 minutes prep, then just let it boil 1+ hours.

If you forget stuff on the fire then yeah go get a burger

I keep my fridge empty of perishables, precisely because things in it have a tendency to rot. Putting the rotting stuff into a rot soup that makes me sick will not increase the amount of stuff in my fridge.