In a medium saucepan, combine the water, butter, sugar, and a pinch of salt, then bring to a boil over medium heat. Once boiling, reduce the heat and quickly add the flour, stirring vigorously with a wooden spatula. Keep stirring until the mixture thickens and pulls away from the sides of the pan. Transfer the dough to a stand mixer bowl or a heatproof bowl and use a paddle attachment to mix, allowing the dough to cool for about 3 to 5 minutes. When the dough has cooled slightly, add the eggs one at a time, mixing continuously; the dough will become much stickier. Next, transfer the churro dough to a piping bag fitted with a star tip—Wilton 1M works well. Pipe 3-4 inch long churros onto a parchment-lined baking sheet, cutting the ends with scissors or a knife. Freeze the piped churros for 30 minutes. About 3 minutes before baking, preheat your air fryer to 360°F. Carefully peel the frozen churros off the parchment and place them in the air fryer basket. Bake for 13 to 14 minutes, adjusting batch size as needed depending on your air fryer’s capacity. Keep any leftover churros frozen to prevent them from softening. In a shallow bowl or plastic bag, mix the sugar and cinnamon. As soon as the churros come out of the air fryer, toss them in the cinnamon sugar mixture to coat evenly. Serve warm with dulce de leche, sweetened condensed milk, or Nutella for dipping!