Preheat oven to 375°. Rub garlic powder over chicken; cut into 1-in. strips. Stuff chicken into manicotti shells. Spread 1 cup spaghetti sauce in each of 2 greased 13x9-in. baking dishes. , Place 8 stuffed manicotti shells in each dish. Sprinkle with sausage and mushrooms. Pour remaining spaghetti sauce over the top. Sprinkle with cheese., Drizzle water around the edge of each dish. Cover and bake 45-55 minutes or until chicken is no longer pink and pasta is tender. Freeze option: Cover and freeze unbaked casseroles for up to 1 month. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 375°. Bake casseroles as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165°.