In a large skillet over medium heat, add a drizzle of oil and sauté the chopped onion until it becomes translucent, about 3-4 minutes.
Add the ground chicken to the skillet with the onions and break it apart as it cooks. Cook for about 5-7 minutes until the chicken is no longer pink.
Stir in the chili sauce or ketchup, brown sugar, yellow mustard, salt, black pepper, and garlic powder. Mix well to coat the chicken in the sauce.
Reduce the heat to low and let the mixture simmer for about 10 minutes.
While the mixture simmers, lightly toast the hamburger buns.
Spoon the chicken mixture onto the toasted hamburger buns and serve immediately.