In a large bowl combine 1 1/2 cups buttermilk, 1/4 cup pickle juice or vinegar, 1 tablespoon hot sauce, 1 1/2 tbsp garlic granules, 1 1/2 tbsp onion granules, 2 tsp paprika, 2 tsp coarse salt, and 1 tsp black pepper; add the chicken tenders and toss to coat. Cover and refrigerate for 2 to 24 hours.
Prepare the dry dredge: in a wide shallow bowl whisk together 1 cup all-purpose flour, 1 cup cornstarch, 1 tablespoon baking powder, 2 tsp garlic granules, 2 tsp onion granules, 2 tsp paprika, 2 tsp salt, and 1 tsp black pepper. Set aside.
Prepare the wet dredge: in another wide bowl whisk 4 large eggs with 1/2 cup buttermilk and 1 teaspoon salt plus 1/2 teaspoon pepper until smooth.
Heat oil in a 4–5 quart heavy pot or deep fryer to 375°F (190°C); use a thermometer to monitor temperature. Fill the pot about halfway with oil.
Working a few tenders at a time, drain excess marinade, then dredge each piece in the dry mixture, pressing to adhere. Shake off excess, dip into the egg wash to fully coat, let excess drip off, then dredge again in the dry mixture and press to create an even coating. Place coated tenders on a wire rack over a sheet tray and rest up to 15 minutes.
Fry the tenders in batches of 4–6 pieces so the oil temperature holds. Lower each piece into the hot oil and cook 3½–4 minutes, turning once or twice, until golden brown and cooked through (internal temperature should be 165°F).
Transfer fried tenders to a wire rack to drain and rest while you finish remaining batches. Serve warm with desired dipping sauces.