Prick sweet potato all over with a fork. Microwave on high in 2-minute intervals until tender, turning halfway through, 8 to 10 minutes. Cool sweet potato until easily handled.
Preheat oven to 375 degrees F (190 degrees C). Line a baking sheet with parchment paper.
Mix white whole wheat flour, whole wheat flour, baking powder, sugar, baking soda, salt, and cinnamon together in a large bowl. Cut in coconut oil with a pastry cutter until mixture is the size of peas.
Peel sweet potato and mash coarsely with a fork. Measure out 3/4 cup mashed sweet potato and mix into the flour mixture. Pour in cashew milk and mix until dough is just sticky.
Dust a flat work surface with flour. Turn out dough and knead 5 to 6 times to bring it together. Pat out to 1/2-inch thickness. Cut into rounds with a biscuit cutter. Place 1 inch apart on the lined baking sheet.
Bake biscuits in the preheated oven until bottoms are golden brown, 12 to 16 minutes.
