Pour enough vegetable oil into a large frying pan to come about 1/2 inch up the sides and heat over medium.
Cut the chicken breasts into 1-inch pieces on a cutting board.
In a mixing bowl, whisk together the all-purpose flour, garlic powder, egg, milk, salt, black pepper, and red chili powder until a thick batter forms.
Dip each chicken piece into the batter, coating evenly, then carefully add to the hot oil without overcrowding the pan.
Fry the chicken pieces until golden brown and cooked through, about 3–5 minutes per side depending on size, turning as needed.
Remove the fried chicken bites with tongs or a slotted spoon and drain on paper towels.
Transfer the drained chicken to a serving plate and drizzle with sweet chili sauce; garnish with chives if desired.
