Rinse and drain canned black beans. Add to slow cooker, along with tomato sauce, diced tomato including juice, and brown sugar.
In a medium bowl, add torn bread and milk. Mash together with fork and then add ground beef and 1/2 tsp black pepper. Mix together with your fingers and break into small pieces before adding to slow cooker pot.
In a microwave safe bowl, add diced onions, taco seasoning, tomato paste, olive oil, and garlic powder. Stir to combine. Microwave at one minute intervals, stirring in between each minute. Heat for a total of 3-5 minutes until onions are softened. Add to slow cooker pot.
Cover slow cooker and set to cook 3-5 hours on high heat or 6-8 hours on low heat. Stir before serving.