In a large bowl, combine cake and dry pudding mixes. Add the eggs, sour cream, water and oil; beat until blended (batter will be thick).
Combine sugar and cinnamon. Spoon half of the batter into 2 greased 8x4-in. loaf pans; sprinkle each with 2 tablespoons cinnamon sugar. Spread with remaining batter; sprinkle with remaining cinnamon sugar.
Bake at 350° for 35-40 minutes or until a toothpick inserted in the centre comes out clean. Cool for 10 minutes before removing from pans to wire racks.