In a stockpot, boil water. Add tomatoes, onions, and radish (if you have them). Simmer for 5 minutes.
Add green peppers, sinigang mix, okra, and green beans. Put in the prawns. Cook for 5 minutes or until the vegetables and prawns are cooked through.
Season the stock with fish sauce and adjust according to your preference.
Add water spinach and turn off the stove. Cooking it off with the heat.