1. In a large pot, add the chicken, water, onion, ginger, salt, and sugar. Bring to a boil.
2. Reduce heat and simmer for 30 minutes, skimming off any foam.
3. Remove the chicken and let it cool. Shred the meat and set aside.
4. Strain the broth and return it to the pot. Adjust seasoning with fish sauce.
5. To serve, place cooked rice noodles in bowls, top with shredded chicken, and pour hot broth over.
6. Garnish with cilantro, green onions, bean sprouts, lime wedges, and Thai basil.