Preheat oven to 400°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, sugar, baking powder, and salt in a bowl. Cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Combine sweet potato and milk in a small bowl; add potato mixture to flour mixture, stirring just until moist.
Turn dough out onto a lightly floured surface; knead lightly 5 times. Roll dough to a 3/4-inch thickness; cut with a 2-inch biscuit cutter into 10 biscuits. Place biscuits on a baking sheet coated with cooking spray. Gather remaining dough. Roll to a 3/4-inch thickness. Cut with a 2-inch biscuit cutter into 6 biscuits. Place the biscuits on prepared baking sheet. Discard any remaining scraps.
Bake at 400° for 15 minutes or until lightly browned. Remove from pan; cool 5 minutes on wire racks. Serve warm or at room temperature.