BRING water to boil in large saucepan. Add chicken and Macaroni; stir. Return to boil.
BOIL 10 to 12 min. or until chicken is done and macaroni is tender; drain. Return to pan.
SQUEEZE Cheese Sauce over hot macaroni mixture; mix well. Add tomatoes; cook on medium heat 3 to 5 min. or until heated through, stirring occasionally.