Stir together flour and pepper in a shallow dish. Lightly beat eggs and water in a second shallow dish. Place panko in a third shallow dish. Dredge avocado wedges in flour, shaking off excess. Dip in egg mixture, allowing any excess to drip off. Dredge in panko, pressing to adhere. Coat avocado wedges well with cooking spray. Place avocado wedges in air fryer basket, and cook at 400°F until golden, 7 to 8 minutes, turning avocado wedges over halfway through cooking. Remove from air fryer; sprinkle with salt. While avocado wedges cook, whisk together ketchup, mayonnaise, vinegar, and Sriracha in a small bowl. To serve, place 4 avocado fries on each plate with 2 tablespoons sauce.