Marinate chicken in buttermilk for at least 30 minutes.
Mix flour, garlic powder, paprika, salt, and pepper in a bowl.
Heat oil in a deep skillet over medium heat.
Remove chicken from buttermilk, letting excess drip off.
Dredge chicken pieces in the flour mixture.
Carefully place coated chicken in hot oil, frying in batches.
Fry until golden brown and cooked through, about 5-7 minutes.
Remove chicken and drain on paper towels.
Mix mayonnaise, sweet chili sauce, and sriracha in a bowl.
Toss fried chicken in the sauce until well coated.