Preheat oven to 375°. In a small heavy saucepan, mix sugar, cornstarch, cinnamon and water until smooth; bring to a boil. Cook and stir until thickened, about 2 minutes. Remove from heat; stir in berries. Transfer to an 8-in. square baking dish coated with cooking spray.
For topping, beat sugar and butter until crumbly. Beat in vanilla and milk. Whisk together flour, baking powder and salt; add to butter mixture, stirring just until moistened. Drop by tablespoonfuls over fruit.
Bake until filling is bubbly and a toothpick inserted in topping comes out clean, 25-30 minutes. Serve warm.