In a large skillet, combine beef, water, mustard, and sugar. Simmer over medium heat until the beef is cooked through, about 5 minutes, breaking up clumps of meat with a spoon.
Drain the fat if desired (I don't, and it is closer to the original recipe if you don't, but you can if you want). Stir in onion and season to taste with salt and pepper (I like 1 teaspoon salt and 1/2 teaspoon pepper).
Serve meat on buns with toppings on the side such as ketchup, mustard, mayonnaise, and pickles.
Ground beef: I prefer a ground beef blend of 85% lean, 15% fat, for the best flavor.
Onions: Yellow onions, white onions, or even shallots will do. I add them after the meat is cooked so they're still a bit raw in the beef, just like a traditional Maid-Rite sandwich. Brown them in the skillet before browning the beef if you like them a little softer and milder in flavor.
Hamburger buns: I love a good quality soft burger bun, toasted, buttered, and ready to go. But you can even make these slightly smaller soft dinner rolls for a buffet-style meal or a tailgate menu.
Yield: This Maid-Rite recipe makes 4 delightfully sloppy sandwiches.
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: Feel free to make the meat up to 3 days in advance, then store in an air-tight container in the refrigerator. Reheat on the stove or in the microwave until warm, then pile inside hamburger buns.
Freezer: Make the loose meat portion, then divvy it up in single-size or family-size servings in freezer-safe containers or zip-top bags. Thaw overnight in the refrigerator, and reheat on the stove or in the microwave.
Slow cooker: To make Loose Meat Sandwiches in a slow cooker, brown ground beef in a skillet, then add to a slow cooker. Add all remaining ingredients except buns to slow cooker. Cover and cook on LOW for 2 to 3 hours. Serve in buns.
Optional seasonings: Some cooks swear by a dash or two of Worcestershire sauce or soy sauce to amp up the flavor.
Take your Maid-Rite over the top: Any burger toppings you like will be a hit atop a Loose Meat Sandwich, too. Try dill pickle slices, red onion, tomato slices, a splash of barbecue sauce, mayonnaise, ketchup, and/or mustard.