In a pan, add water, butter, salt, and sugar. Bring it to a boil over high heat.

Reduce the heat and add in the flour gradually, mixing until the dough comes together. Switch off the flame.

Remove the dough from the pan into a large mixing bowl and allow it to cool down for 4-5 minutes.

Add in the egg and vanilla extract and mix everything together with an electric hand mixer.

Transfer the mixture into a piping bag. Preheat the air fryer to 375°F. Spray the basket with a neutral nonstick cooking spray.

Pipe bite-sized churros into the air fryer without overcrowding. Cook in several batches or drop them by the spoonful.

Brush some butter on top of the churros and cook for 12-15 minutes until golden brown.

In a shallow bowl, mix together sugar and cinnamon.

Once the churros are done, transfer them into the sugar and cinnamon mixture. Toss to coat evenly.

If the mixture is not sticking well, brush the churro bites with melted butter or spray with nonstick cooking spray, then roll into the cinnamon sugar mixture.