Preheat oven to 400 degrees F (200 degrees C). Spray a 9×13-inch baking pan with cooking spray.
Stir together tomatoes, water, garlic, and stuffing mix in a large bowl; set aside to soften. When dressing is softened, combine all ingredients including chicken and one cup cheese in a large mixing bowl and fold together.
Spread all in sprayed baking pan, top with remaining cup of cheese. Bake uncovered until the chicken cubes have turned white and are no longer pink in the center, about 35-40 minutes.