Heat rice according to package directions.
In a microwave-safe cup, stir rice, milk, cheddar cheese, cream cheese, garlic powder and mustard powder, if desired.
Microwave on high, stirring occasionally, 2 minutes, or until heated through and cheese is melted and saucy.
Tips: For extra-cheesy rice, add 2 tablespoons grated Parmesan cheese.
Substitute garlic powder with 1/2 clove minced garlic.