Preheat oven to 350°. In a large skillet, cook and crumble beef over medium heat until no longer pink; drain. Stir in taco seasoning and water. Add taco sauce; simmer until slightly thickened, 5-10 minutes.
Cover the bottom of a 13x9-in. baking dish with 3 tortillas, tearing them into pieces as necessary. Layer half the meat mixture over tortillas; sprinkle with half the cheese. Layer with 3 more tortillas; spread with refried beans. Cover with sour cream; sprinkle with green onions and olives. Layer remaining tortillas over top; cover with remaining meat mixture and cheese. Bake until heated through, 25-30 minutes. Let stand a few minutes before serving. If desired, serve with chopped tomatoes and avocados.