In a big pot, heat oil over medium heat.
Add onions and tomatoes. Saute until onion is translucent.
Add kimchi and sauté for another 2 minutes.
Add water, sinigang mix, gochujang and pork belly. Combine well. Bring to a boil.
Reduce heat to low and simmer for one hour.
Add string beans and cook for another 2 minutes.
Add fish sauce. Serve into bowls and enjoy!
Inspired by Pepper.ph.