In a large bowl combine 1 1/2 cups buttermilk, 1/4 cup pickle juice or vinegar, 1 tablespoon hot sauce, 1 1/2 tablespoons garlic granules, 1 1/2 tablespoons onion granules, 2 teaspoons paprika, 2 teaspoons coarse salt, and 1 teaspoon ground black pepper; add the chicken tenders, mix to coat, cover, and refrigerate for 2 to 24 hours.
Whisk together the dry dredge in a wide shallow bowl: 1 cup all-purpose flour, 1 cup cornstarch, 1 tablespoon baking powder, 2 teaspoons garlic granules, 2 teaspoons onion granules, 2 teaspoons paprika, 2 teaspoons coarse salt, and 1/2 teaspoon ground black pepper; set aside.
In a separate wide bowl whisk 4 eggs with 1/2 cup buttermilk, 1 teaspoon coarse salt, and 1/2 teaspoon ground black pepper to make the egg wash; set aside.
Heat enough oil in a 4- or 5-quart pot to come about halfway up the sides and bring to 375°F, monitoring with a candy or instant-read thermometer.
Working a few tenders at a time, drain excess marinade, dredge each tender in the seasoned flour mixture pressing to coat, then dip completely in the egg wash, let excess drip off, and dredge again in the flour mixture; place coated tenders on a wire rack set over a sheet tray and rest up to 15 minutes.
Fry the tenders in batches (do not overcrowd) at 375°F; the temperature will drop to about 350°F—adjust heat to maintain the oil. Cook 4 to 6 tenders at a time for 3 1/2 to 4 minutes, turning once or twice, until golden brown and cooked through.
Transfer cooked tenders to a wire rack to drain while you finish the remaining batches.
Serve hot with optional dipping sauces such as ranch, blue cheese, or honey mustard.