Brown meat in large skillet add onion and cook until translucent and soft. Season with salt and pepper and drain off any fat.
Place in slow cooker. Add water and ketchup. Add mustard, sugar and onion powder if using. Stir to combine. Cover and cook on low 4-5 hours or on high 2-3 hours.
Freezer instructions: Cool completely in refrigerator. Label container and freeze. When ready to use thaw in fridge overnight or until thawed. Heat in skillet over low heat until heated through and bubbly. Serve.