In a pot over medium heat, heat oil.
Add onions and garlic and cook until softened.
Add tomatoes and continue to cook, mashing with the back of a spoon, until slightly softened.
Add fish sauce and cook, stirring occasionally, for about 1 to 2 minutes.
Add sardines and water. Bring to a boil.
Add miswa and cook, stirring occasionally, for about 2 to 4 minutes or until noodles are just softened.
Season with salt and pepper. Serve hot.