Bake cake according to instructions on box in a 9x13" inch baking pan.
Let cake cool completely then use a fork and poke multiple times throughout the cake.
Mix together the milks then pour over top of the cake slowly, letting it absorb slightly before pouring more. It will seem like it's too much but the cake will definitely soak it all up!
Cover and transfer to the fridge for 3 hours.
Once chilled, spread Cool Whip/Dream Topping on top and sprinkle with cinnamon powder.