Submerge the chicken tenderloins in the pickle brine, cover, and refrigerate for at least 30 minutes and up to 1 hour.

Whisk together the flour, powdered sugar, salt, black pepper, paprika, garlic powder, and celery salt in a shallow bowl. In a separate bowl, beat the egg into the milk until smooth.

Remove chicken from brine without patting dry. Dredge each piece in flour, dip in the milk and egg wash, then press back into the flour. Rest on a wire rack for 5 minutes.

Heat 2 to 3 inches of vegetable oil in a heavy pot to 350°F (175°C). Fry tenders in batches of 3 to 4 for 4 to 5 minutes, turning once, until deep golden brown and the internal temperature reaches 165°F (74°C). Return oil to 350°F between batches and rest finished tenders on a wire rack.

Arrange tenders on a platter, sprinkle with salt, and serve immediately with your choice of dipping sauces.