Combine cake mix, eggs, sour cream, oil and water in a large bowl. Stir until batter is smooth.
In separate bowl, stir together brown sugar and cinnamon.
Next, pour 1/2 the batter into pan.
Then sprinkle brown sugar mixture over the batter.
Pour remaining batter over the cinnamon mixture and gently swirl the batter a few times.
Bake until golden brown, about 40 minutes. (be sure to check center)
For Icing Glaze
Stir powdered sugar, milk and vanilla together to make a smooth runny glaze.
When cake comes out of oven poke holes in it, I use a metal kabob skewer. Then immediately pour icing over the cake while it is still hot. Allow to cool slightly before serving. Enjoy!! (Best served warm!)