Heat a large skillet over MED to MED-HIGH heat with a small drizzle of oil. Add ground beef and onion and cook 5-6 minutes, until beef is cooked through, crumbling as you cook. Drain meat/onion mixture and return to skillet.
Reduce heat to MED-LOW, add garlic and cook 1-2 minutes. Add marinara sauce, diced tomatoes, water, Italian seasoning, balsamic vinegar, thyme, basil, oregano, salt, pepper, and sugar. Stir to combine well.
Spoon meat mixture into lightly greased 6 quart slow cooker. Top with broken spaghetti and stir together. Top with shredded cheese, cover and cook on LOW 4 hours.
Serve garnished with fresh parsley or basil and a sprinkle of grated Parmesan cheese if desired.
