Freeze the cheese sticks. Unwrap the string cheese and cut each stick in half crosswise. Place on a parchment-lined baking sheet in a single layer and freeze for 30–60 minutes until completely solid. Do not skip this step — starting from frozen is what prevents the cheese from blowing out before the crust sets.
Crush the Cheetos. Seal the Cheetos in a zip-lock bag and crush with a rolling pin until they reach a coarse, panko-like crumb. Do not crush to a fine powder — you want texture. Transfer to a shallow bowl.
Set up your dredging station. Arrange three shallow bowls: Bowl 1 with flour (and garlic powder if using), Bowl 2 with beaten eggs, Bowl 3 with crushed Cheetos.
Double-coat every stick. Working one at a time, coat each frozen stick in flour, dip in egg, then roll in Cheetos crumbs. Immediately repeat — dip in egg again, then roll in Cheetos a second time. Press gently so the coating adheres fully. Place back on the baking sheet.
Second freeze. Freeze the coated sticks for at least 30 minutes, or up to overnight. This is the step that locks the crust solid before it hits the heat. At this point the sticks can be transferred to a sealed freezer bag and kept frozen for up to 2 months.
Preheat the air fryer. Preheat to 390°F (200°C) for 3–5 minutes. Spray the basket with cooking spray.
Air fry. Place the frozen coated sticks in a single layer in the air fryer basket, making sure they are not touching. Lightly spray the tops with cooking spray. Air fry for 4–6 minutes until the coating is deeply golden and the cheese is just beginning to ooze at the ends.
Rest and serve. Allow to rest for 1 minute before serving — the cheese will be extremely hot straight out of the air fryer. Serve immediately with marinara, ranch, or sriracha mayo.