Using a hand blender, in a large bowl, add sugar and oil, blend until combined. Add eggs one at a time, vanilla extract, sweet potato puree, and cinnamon, blend well.
In a bowl, add flour, baking powder and salt, mix well.
In thirds, add dry ingredient, alternately with milk.
In a Bundt pan add cooking spray, add ½ sweet potato mixture
With remaining sweet potato mixture, add cocoa powder, blend well.
Add Cocoa sweet potato mixture in Bundt pan, swirl mixture with a knife, for marble effect.
Place in oven at 375 degrees for 50-55 minutes, insert a toothpick in middle, if toothpick comes out dry, loaf is ready. Let cool for 15 minutes, and ready to serve.