Pour enough vegetable oil into a frying pan to cover the bottom by about 1/4 inch and heat over medium heat until shimmering.
Cut the chicken breasts into 1-inch pieces and set aside.
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.
Working in batches to avoid overcrowding, dip each chicken piece into the batter, allowing excess to drip off, then place into the hot pan.
Fry the chicken pieces until golden brown on all sides and cooked through, about 3–5 minutes per batch depending on size.
Use tongs or a slotted spoon to transfer the cooked chicken to a plate lined with paper towels to drain excess oil.
Transfer the drained chicken bites to a serving plate and drizzle evenly with the sweet chili sauce.
Garnish with chives if desired and serve immediately.