Combine mung beans and one cup of water. Soak for an hour.
Drain mung beans and combine with two cups of water in a pot. Boil and simmer until mung beans are soft. Mash the mung beans using the back of your wooden spoon. Stir until water almost dries out and set a side.
Using the same pot, sauté garlic, onion and tomatoes in olive oil. Add half cup of water and bring to a simmer for 5 minutes. Then, mash the tomatoes using the back of the wooden spoon.
Add the mashed mung beans, remaining water, canned sardines and bouillon cube. Stir and let it simmer for 5 minutes.
Season with ground black pepper and fish sauce.
Add the alugbati and simmer for another 3 minutes.