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

Reduce the heat and add in the flour gradually, mix 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. Pre-heat the air fryer to 375F degrees. Spray the basket with a neutral nonstick cooking spray (I think coconut oil spray works best in the air fryer.) 

Pipe bite-shaped churros on the air fryer carefully without overcrowding. You’ll have to cook in several batches. Note: you could also just drop them by the spoonful into the air fryer basket. 

Brush some butter on top of the churros and cook for 12-15 minutes until golden brown (see notes below). Repeat with rest of the dough. In a shallow bowl mix together sugar and cinnamon powder.

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

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

Serve with chocolate syrup, honey or Nutella.