In 12-inch skillet, brown beef and onion over medium-high heat, stirring frequently, until thoroughly cooked; drain.
Stir in garlic, tomatoes and spinach; cook 2 minutes, stirring occasionally.
Stir in sauce mix (from Hamburger Helper box) and hot water until dissolved. Stir in milk and uncooked pasta (from Hamburger Helper box). Return to heat; heat to boiling.
Reduce heat; cover and simmer about 12 minutes, stirring occasionally, until pasta is tender. Stir in cheese.