In a large bowl, combine chicken pieces with the milk and pickle juice. Stir, cover, and place in the refrigerator for at least 60 minutes.
Preheat your air fryer to 390 degrees F and completely coat the fryer basket with cooking oil. (If you have a dark coating on your air fryer basket use an olive oil spray.)
In a shallow bowl combine the flour, powdered sugar, onion powder, salt, garlic powder, paprika, and pepper.
Beat the egg with a fork and add it to the chicken mixture, stirring to combine.
With a slotted spoon, remove some of the chicken pieces from the marinade, letting the liquid drain from the spoon. Then add the chicken to the flour mixture. Coat the chicken and then place them on the tray of the air fryer. (You'll need to cook in batches.)
Spray the chicken well with cooking spray and place in the air fryer for 5 minutes. Shake the chicken after 5 minutes and spray any floured parts with cooking spray. Cook for another 3-5 minutes until the chicken is crispy and golden brown.