Combine sugar with the cinnamon, if using, in a shallow bowl.; set aside. Or simply set aside plain sugar.

Grate the apple; set aside in a fine mesh strainer over a bowl. Set out a plate lined with paper towels. Whisk together the flour and baking soda; set aside.

In a small saucepan whisk together the water, sugar, and butter. Bring this mixture to a boil over medium-high heat. Remove the pan from the heat and turn off the heat.

Add the flour mixture to the saucepan and beat very quickly using a wooden spoon until the dough removes itself from the sides of the pan and forms into a ball or one mass.

Transfer to a food processor. Add eggs one at a time, and mix thoroughly after each addition. This dough is called pate choux.

Squeeze the juice from the apples by pressing them against the mesh strainer allowing the juice to drip into the bowl. Squeeze in your hands as well. Save the juice for another use. Transfer the grated apple to the dough and fold in using the paddle attachment (if you have one).

Refrigerate the dough for 45 minutes, covered, or inside a piping bag or decorating device. (Chilling helps aid browning.)

When the dough has 15 minutes left to chill, preheat at least 1 quart of oil in a deep-fryer, Dutch oven/deep pot, or deep skillet to 350°F or 2 cups of oil in a small, deep saucepan over medium-high heat.

If not already done, add the dough to a piping bag or piping device, fitted with a small star tip for minis and a large star tip for standard size churros. Working in small batches, pipe short or long strips of dough into the oil. If you cannot get the dough to release into the oil, use kitchen scissors to cut it off. Do not over-crowd the oil as this prevents browning and lowers the oil's temperature. Fry on one side until they reach your desired crispness and color, about 10 - 20 seconds. Flip them over and cook until they are golden brown on all sides.

Remove the churros using metal tongs or a metal slotted spoon, allowing excess oil to drip back into the hot oil. Transfer churros to the paper towel-lined plate to drain.

If desired, once slightly cooled, but still warm, roll churros in cinnamon sugar. Serve immediately. Store any leftovers in a resealable storage bag with a paper towel to absorb moisture for up to 24 hours. Freeze any that you will not consume within one day. Allow frozen churros to defrost at room temperature.