Use either a deep fryer or a large deep skillet. Be sure to add enough of oil to line the bottom of the pan a couple of inches deep. Make sure the oil heats up to 350 degrees before frying. Pour sugar into a small bowl. You will dredge the donuts in the sugar after they have been removed from the oil.
Allow the donut to brown on one side, turn over. This should take about 90 seconds. Be sure to fry only a couple at a time, or the oil may cool too much, and the donuts will absorb too much oil.
When golden brown on both sides remove from oil and drain on paper towels or a wire rack. When the donuts have cooled for about 15 seconds dredge in the sugar.