Preheat oven to 350 degrees.
In a large bowl, mix together spice cake mix, milk, butter, eggs, and pumpkin puree until smooth. Pour into a greased 9x13" casserole dish.
Bake for the recommend time on the spice cake mix box (usually 30-40 minutes).
Allow cake to cool. Once cool, use a fork to poke holes all over surface of the cake.
In a bowl, whisk together 8oz heavy cream, sweetened condensed milk, and coffee creamer. Pour mixture over top of cooled cake. Allow mixture to soak in for 30 minutes to an hour.
Whip remaining heavy cream with a mixer. Gently fold in powdered sugar. Spread whipped cream over cake.
Sprinkle cinnamon on top.