Heat the oven to 325 degrees. Spray a 13 x 9-inch non-stick baking pan with cooking spray, dust lightly with flour; tap out extra flour; set aside. In a large bowl, beat the cake mix, water, ½ cup light sour cream, vegetable oil, and eggs on low speed for 30 seconds. Increase the speed to medium high; continue beating, scraping the bowl often, for 2 additional minutes. Pour the batter into the prepared pan. Bake for 25 to 30 minutes or until a wooden pick inserted in the center, comes out clean. Remove the cake from the oven. Using a fork, poke holes over the entire cake. In 4-cup measuring cup, using a wire whisk, stir together the sweetened condensed milk, 1 cup heavy whipping cream, and ¼ cup light sour cream. Slowly pour the milk mixture over the cake in the pan. Cover the cake and refrigerate for 1 to 1 ½ hours or until the mixture is absorbed into cake. Remove the cake from the refrigerator. In a medium bowl, beat the remaining 1 cup whipping cream until soft peaks form (1 to 2 minutes). Slowly add the confectioners’ sugar to the whipped cream. Continue beating, scraping the bowl often, until stiff peaks form (an additional 1 to 2 minutes). Frost the top of the cake with the whipped cream mixture. Sprinkle the cake lightly with the cinnamon. Refrigerate leftovers.