Add garlic, onion, and ground beef to a large skillet. Break it up into chunks with a spoon or spatula while cooking. Cook until browned. Then, drain the excess fat.
Add taco seasoning, diced tomatoes, and water. Mix to combine. Then, add spaghetti. Be sure that spaghetti is covered with the liquid. Bring to a boil. Then, reduce heat to low and cover skillet with a lid. Simmer for 12-15 minutes or until spaghetti is cooked, stirring occasionally.
Remove the lid. Cook for a few minutes more or until excess liquid evaporates. Turn off the heat.
Add shredded cheddar cheese. Then, cover the skillet with a lid again. Let the cheese melt. Add chopped fresh parsley and serve immediately. Enjoy!