Mix the cake mix, pudding, milk, bananas, sour cream and eggs for a couple minutes with an electric mixer.
Pour half of the batter in the bottom of a greased 9x13 pan.
In a small bowl, combine the sugar, walnuts and cinnamon.
Sprinkle half of the sugar mixture over the cake mixture.
Add the rest of the batter and sprinkle with remaining sugar.
Bake at 350 degrees for 35-40 minutes or until done.