Preheat oven to 350º degrees. Grease a 9"x13" baking dish.
In a small bowl, combine sugar and cinnamon; using a spoon, mix well; set aside.
In a large mixer bowl, cream together butter, sugar and eggs until light and fluffy.
Add milk, flour and baking soda.
Put 1/2 of batter (or a little less) into the prepared 9"x13" greased baking dish.
Sprinkle 3/4 of cinnamon-sugar mixture on top of the 1/2 batter.
Add remaining batter to baking pan.
Sprinkle with the remaining cinnamon-sugar mixture; swirl with a knife.
Bake in 350º oven for 45-50 minutes or until toothpick tester comes out clean.
Cool in pan for approximately 10-15 minutes.