Preheat oven to 350 degrees. Grease the bottom of a 9-inch by 13-inch pan.
In a large bowl, whisk together cake mix, water, oil, and egg whites. Reserve 1 cup of the batter. Pour the remaining batter into the prepared pan.
In the reserved batter, mix in the allspice and the cinnamon. Drop mounds of spiced batter into pan, and swirl using a toothpick. Bake until cake begins to separate from the sides of the pan, and a toothpick inserted into the center comes out clean, about 28 to 30 minutes.
Cool cake prior to frosting, about 1 hour.
Meanwhile, in a standing mixer, beat the heavy cream, powdered sugar, allspice and cinnamon on medium high speed until stiff peaks form. Once the cake has cooled, frost and garnish with crushed root beer candies.