In a large bowl, mix together cake mix, milk, butter, and eggs. Pour into a greased 9x13" pan and bake according to package instructions.
While cake bakes, mix together half of the heavy cream, evaporated milk, and sweetened condensed milk.
Once cake is baked and allowed to cool for 10-15 minutes, use a fork to poke holes all over the cake. A little bit at a time, pour milk mixture over the cake, allowing it to soak in before pouring additional mix. Continue until all milk is poured and soaked in.
Use other half of the heavy cream to make whipped cream; mix powdered sugar in slowly as you beat heavy cream with a mixer. Beat until stiff peaks form.
Spread whipped cream over top of the cake. Sprinkle cinnamon to over the top of the whipped cream. Refrigerate cake for about an hour before serving.