Combine sugar, soy sauce, water, garlic, and ginger in a large stock pot; stir until sugar is dissolved. Place chicken in stock pot and bring to a boil. Using tongs, turn chicken in pot every 5 minutes.
Boil chicken until no longer pink at the bone and juices run clear, about 35 minutes. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C). Sauce mixture will turn into a rich, brown glaze. Remove pot from heat and let cool 10 minutes.
Place chicken on a platter and sprinkle with chopped green onions.