In a medium bowl, combine the buttermilk and shrimp. Let it marinate for at least 30 minutes in the refrigerator.

In another bowl, mix the flour, garlic powder, paprika, salt, black pepper, and cayenne pepper.

In a third bowl, place the panko breadcrumbs.

Remove the shrimp from the buttermilk, allowing excess to drip off. Dredge each shrimp in the flour mixture, then dip back into the buttermilk, and finally coat with panko breadcrumbs.

Heat about 1 inch of vegetable oil in a large skillet over medium-high heat. Once hot, carefully add the shrimp in batches, frying until golden brown and cooked through, about 2-3 minutes per side. Remove and drain on paper towels.

In a small bowl, whisk together the mayonnaise, sweet chili sauce, sriracha, and lime juice.

Serve the shrimp hot, drizzled with the sauce or served on the side for dipping.