1Preheat oven to 350 degrees F (175 degrees C). Grease a 13x9-inch baking dish.
2Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease.
3Mix browned beef, pork and beans, cold water, white vinegar, and mustard together in the prepared baking dish.
4Bake in preheated oven until beginning to dry around the edges, about 1 hour.