1. Heat oil in a sauce pan, over medium heat. Add onion and then add the garlic. Saute until limp. Add the tomatoes. Put the squash. Saute until the squash is half cooked. Pour the fish sauce and stir for 1 minute.
2. Add the water and sardines. Bring to a boil. Add the sotanghon, stirring occassionaly for about 2 or 3 minutes or until the sotanghon noodles just softened.
3. Season with salt and pepper. Add the petchay. Let simmer for 2 minutes.