Trim excess fat and skin from the 2 large chicken breasts, if there are any, and cut them in half.
Put the chicken breasts in a bowl (or a storage bag) with both the pickle juice and water. Let the mixture sit for at least 1 hour, though overnight works best for maximum flavor absorption.
In a mixing bowl, add all the dry ingredients: all-purpose flour, cornstarch, salt, pepper, granulated sugar, paprika, and chili powder. Mix well.
In a separate bowl, mix the milk and egg together.
Take the marinated chicken and dip each in the flour mixture.
Next, dip them in the egg wash.
Dip the chicken breasts in the flour mixture once again.
Place a piece of parchment paper in the air fryer basket and lay the coated chicken breasts on it. Apply cooking spray to the meat.
Cook the chicken breasts at 380°F for about 16 to 18 minutes, making sure to flip the chicken halfway. Cook them until their internal temperature reaches 165°F and the breading looks golden brown and crispy.
Remove the chicken fillets from the air fryer basket and set them aside.
Cut your biscuits in half. If desired, you can warm the biscuits in the oven for a bit.
Place the chicken breast between the biscuits, serve, and enjoy!