In a small saucepan over medium heat, combine water, butter, 1 tbsp sugar, and salt. Bring to a rolling boil. Remove from heat and, using a wooden spoon, stir in the flour until the mixture forms a smooth ball.

Let the dough cool for 5 minutes. Add the beaten egg and stir vigorously until the egg is fully incorporated and the dough is smooth and glossy.

Transfer the dough to a piping bag with a star tip or a zip-top bag with a corner snipped off. Pipe 1-inch long segments onto a parchment-lined plate or baking sheet. For an alternative method, you can use canned biscuit dough cut into 6-8 pieces per biscuit.

Preheat your air fryer to 375°F (190°C). Lightly spray the basket with cooking oil. Place the churro bites in a single layer in the basket, ensuring they are not overcrowded. Air fry for 5-7 minutes, shaking the basket halfway, until golden brown and puffed.

In a medium bowl, mix 1/2 cup of granulated sugar and the ground cinnamon. As soon as the churro bites are done, brush them with melted butter and immediately toss them in the cinnamon-sugar mixture until well coated. Serve warm.