Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, whisk together the mashed sweet potato, sugar, melted coconut oil, egg, and vanilla extract until smooth.
In a separate bowl, sift together the flour, baking powder, baking soda, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. The dough will be slightly sticky.
In a small bowl, combine the granulated sugar and a teaspoon of cinnamon for rolling.
Using a tablespoon, scoop dough and roll into balls, then roll each ball in the cinnamon-sugar mixture until coated.
Place the dough balls onto the prepared baking sheet about 2 inches apart, and gently flatten each slightly with your palm.
Bake for 10-12 minutes, or until the edges are set but the centers remain soft.
Remove from oven and allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.