You can use a sealable bag or a large bowl to brine the chicken. Add the chicken breasts to the bowl or sealable bag along with the pickle juice and buttermilk. Refrigerate for 30 minutes.
Add the flour, paprika, garlic powder, salt, pepper, and sweetener to a large bowl, large enough to dredge the chicken. Stir to combine.
Add the egg to a bowl large enough to dredge the chicken.
Spray the air fryer basket with cooking oil.
Remove the chicken from the marinade and dredge both breasts in the beaten egg and then the flour. Place the chicken in the air fryer basket. (The use of the egg is optional and will help keep the breading intact on your sandwich. I often make this without using the egg).
Spritz the top of the chicken with peanut oil. Spray from a distance.
Air fry on 400 degrees for 15 minutes.
Open the air fryer and flip the chicken. Be careful with tongs. You don't want to lose any of the breading on the chicken. Your chicken may be fully cooked at this point and you may only need a couple of minutes to crisp this side of the chicken. Spritz this side of the chicken.
Air fry for an additional 5-7 minutes until the chicken is crisp. You should also use a meat thermometer to ensure the chicken has reached an internal temperature of at least 165 degrees.
Every air fryer model and brand will cook at varying speeds. Monitor your results carefully, and adjust as needed.
For toasted buns, toast the buns for 3-4 minutes on 400 degrees.
Remove the chicken from the air fryer and assemble the sandwich.