Preheat oven to 325°F. Grease 9x13" pan.
Mix cake mix, sour cream, water, oil and eggs in a large bowl.
In a smaller bowl, stir together brown sugar and cinnamon.
Layer half of batter in pan, then half the cinnamon mixture, then remaining batter, then top with remaining cinnamon mixture.
Bake for 45 to 55 minutes or until toothpick inserted in middle comes out clean. Cool.