Mix baking mix, brown sugar, and pumpkin pie spice together in a large bowl. Beat milk, mashed sweet potatoes, white vinegar, and 2 tablespoons vegetable oil together in a separate bowl until smooth; gradually beat into the dry mixture to incorporate into a batter.
Heat a large skillet over medium heat; add just enough oil to cover the cooking surface and let oil get hot. Pour batter onto hot skillet by 1/4 cup portion, taking care to not overcrowd the skillet. Cook pancakes until browned, 3 to 5 minutes per side. Repeat cooking steps until all batter is used.
