In a large saucepan, heat 3 inches of canola oil to 375° and top 2 baking sheets with racks. Keep the doughnuts chilled. Add one-third of the scraps at a time to the hot oil and fry, turning once, until browned, about 2 minutes per batch. Using a slotted spoon, transfer the scraps to a rack. Let the oil return to 375°. Add the doughnut holes and fry, turning occasionally, until browned all over, 1 to 2 minutes. Using a slotted spoon, transfer to a rack. Toss the doughnut scraps and holes in the cinnamon-cardamom sugar until coated and transfer to a platter.