Preheat the oven to 350 degrees.
Mix together the cake mix, sugar, oil, water, eggs, pumpkin puree, pumpkin pie spice, and cinnamon. Stir for 2 minutes until the batter is smooth.
Pour the batter into a greased 9x13 pan and bake for 25-30 minutes (approx. according to package directions) until a toothpick comes out mostly clean.
Allow the cake to cool for about 10 minutes.
Poke the cake all over the top with the bottom of a wooden spoon.