Preheat oven to 400 degrees.
Spray a 1-quart shallow baking dish with nonstick spray.
Beat the egg with the water in a shallow bowl.
Combine the breadcrumbs, cheese, garlic powder, and pepper in a bowl. Pour onto a sheet of wax paper.
Dip the chicken breasts first in the egg mixture and then lightly coat on both sides with the breadcrumb mixture. Shake off the excess. Place chicken pieces in the baking dish.
Bake until cooked through, golden, and crisp-edged, about 30 minutes. Check to make sure it doesn’t overcook.
One breast per serving.
Serve with marinara sauce.