Unwrap cheese sticks. Cut each in half (24 pieces total).
Set up three shallow bowls for breading.
First bowl: add flour.
Second bowl: whisk eggs and milk.
Third bowl: mix bread crumbs, Parmesan, garlic powder, Italian seasoning, and salt.
Coat cheese stick in flour. Shake off excess.
Dip in egg mixture. Let excess drip off.
Roll in bread crumbs. Press crumbs on well.
Dip back in egg mixture.
Roll in bread crumbs second time. Double breading prevents leaks.
Place on parchment-lined baking sheet.
Repeat with all cheese sticks.
Freeze on baking sheet at least 30 minutes. This is crucial.
Preheat air fryer to 390°F for 3 minutes.
Remove cheese sticks from freezer. Spray with cooking spray on all sides.
Arrange in single layer in air fryer. Do not let them touch. Work in batches.
Air fry at 390°F for 6 to 8 minutes until golden brown. Check at 6 minutes.
Let cool 1 to 2 minutes. Cheese is very hot.
Serve hot with marinara sauce.