In a mixing bowl, combine the chicken pieces with pickle juice. Cover and refrigerate for at least 30 minutes to marinate.
In another bowl, whisk together the flour, powdered sugar, salt, black pepper, paprika, garlic powder, onion powder, and cayenne pepper (if using).
In a separate bowl, combine the milk and egg, whisking until well blended.
Remove the marinated chicken from the pickle juice and pat dry with paper towels.
Heat vegetable oil in a deep frying pan or Dutch oven to 350°F (175°C).
Dredge each piece of chicken in the flour mixture, shaking off excess, then dip into the milk-egg mixture, and finally coat again in the flour mixture. Ensure each piece is evenly coated.
Carefully place the coated chicken nuggets into the hot oil, frying in batches to avoid overcrowding. Fry for 3-4 minutes on each side or until golden brown and fully cooked (internal temperature should reach 165°F or 74°C).
Remove the fried chicken nuggets and place them on a plate lined with paper towels to absorb excess oil.
Serve hot with your favorite dipping sauces.