Manwich is pretty nasty shit and you can make your own super basic sloppy joe with just a little ketchup, brown sugar, and lemon juice. Add it right in the pan after you've browned the meat. This way you can control the sweetness and the sauciness. If you wanna get fancy you can also add a little soy sauce, garlic and onion powder, and maybe some liquid smoke or smoked paprika for some extra depth.
It's basically meat sauce between burger buns. I haven't had one in ages, but they would make frequent appearances in grade school cafeterias and other events involving large amounts of children needing to be fed with low effort. I remember quite liking them; it's basic, but great comfort food, and easy to eat.