Heat a large skillet over medium heat. Add the ground beef, Italian sausage and onion and cook until browned. Once done, drain any excess fat or liquid.
Carefully transfer the meat mixture to the crock pot. Add all of the remaining ingredients except the sugar to the pot and mix to combine.
Cook on low for 3-8 hours. Before serving, stir in the sugar, then serve over spaghetti or other pasta.
