Coat a nonstick skillet with cooking spray; add oil. Place over medium-high heat until hot. Add green onions and garlic; saute 2 minutes. Add water and next 3 ingredients; bring to a boil. Reduce heat; simmer, uncovered, 10 minutes.
Wrap tortillas in aluminum foil; bake at 325° for 12 minutes. Combine 1/4 cup tomato sauce mixture, chicken, and 1 tablespoon of each cheese. Spoon chicken mixture evenly down center of tortillas; roll up tortillas.
Spread 1/4 cup tomato sauce mixture in an 11- x 7- x 1 1/2-inch baking dish coated with cooking spray. Arrange tortillas, seam side down, over sauce. Top tortillas with remaining tomato sauce mixture. Cover and bake at 350° for 20 minutes. Sprinkle with remaining cheese. Bake, uncovered, an additional 5 minutes. Top with sour cream.