Preheat your air fryer. Set it to 375°F (190°C) for about 3 minutes. A warm basket helps the sticks crisp up right away.
Cut the bread. Slice each piece into 3 or 4 even sticks.
Thick bread holds the custard without getting mushy.
Make the custard. Whisk eggs, milk, vanilla, cinnamon, salt, and sugar (if using) in a shallow dish until smooth and well combined.
Dip quickly, don’t soak. Dip each stick in the custard, turning to coat. Let excess drip off. Aim for lightly saturated, not soggy.
Grease the basket. Lightly spray or brush the air fryer basket with oil or melted butter to prevent sticking.
Arrange in a single layer. Place the soaked sticks in the basket with a little space between each one.
Avoid stacking.
Air fry. Cook at 375°F (190°C) for 7–9 minutes, flipping halfway. They should be golden brown and slightly firm to the touch.
Optional cinnamon-sugar finish. While hot, toss the sticks in a cinnamon-sugar mix for a churro-style crunch.
Serve warm. Plate with maple syrup, a dusting of powdered sugar, or berries. Eat right away for the best texture.