In a pan, combine water, butter, salt, and sugar. Bring the mixture to a boil over high heat.

Once boiling, reduce the heat and gradually add in the flour, stirring continuously until the dough comes together smoothly.

Turn off the heat and remove the pan from the stove.

Transfer the dough from the pan into a large mixing bowl and let it cool down for about 4-5 minutes.

Once slightly cooled, add in the egg and vanilla extract. Use an electric hand mixer to thoroughly combine the ingredients until a smooth mixture is achieved.

Transfer the churro dough into a piping bag. Preheat your air fryer to 375°F (190°C).

Spray the air fryer basket with a neutral nonstick cooking spray.

Carefully pipe bite-sized churros into the basket, ensuring not to overcrowd them.

Lightly brush some butter on top of the churros and cook them in the air fryer for 10-12 minutes until they turn golden brown.

Once cooked, transfer them into a cinnamon sugar mixture and toss to coat.