In a heavy pot or saucepan, heat 2 inches of oil over medium-high heat until the oil reaches 375 degrees.
In a brown paper lunch bag, mix together sugar and cinnamon. Set aside.
While the oil is heating, prepare the donut dough by mixing the dry ingredients in a small bowl, then adding the wet ingredients to the dry and stirring until combined. (Don't overmix.)
Measure about 3/4 of a cookie scoop of dough (about 1 tbsp) and drop it into the hot oil.
Use tongs to turn it until it's evenly golden brown on all sides.
Remove it from the hot oil with tongs and drop it into the bag of cinnamon and sugar.
Shake the bag until the donut hole is coated, then set it on a serving dish.
Repeat until all the dough has been used. They are best served warm.
Notes
Your donut holes will double in size when fried, so be sure to use only half the dough of the desired size donut that you wish to make.
The temperature of the frying oil is key to a great donut. Use a thermometer to ensure that the oil is 375°F. You want the donut hole to turn golden brown after about 1 minute in the oil. If it cooks too quickly, the inside will remain raw. If it cooks too slowly, the donut hole will be greasy.
If you don't have a thermometer, add a small amount of batter to the oil. It should bubble quickly, then the bubbles will die down, and it should turn golden after about 45 seconds in the oil.