Make anchovy broth with 8 cups of water. See the recipe.
Rinse the soybean sprouts a couple of times, discarding any skins that are floating. Slice the kimchi into about 1/2-inch thick strips.
Add the sliced kimchi, kimchi juice, gochugaru, and the soup soy sauce (or saeujeot, salted shrimp) to the anchovy broth. Bring it to a boil. Cook over medium high heat until the kimchi turns translucent, about 5 minutes.
Add the bean sprouts and garlic. Cook, covered, for 3 - 4 minutes. Do not open the lid while the bean sprouts are being cooked, or the raw bean smell will linger even after cooked. Once the bean sprouts are cooked, adjust the seasoning, if needed, by adding salt and pepper.
Add the scallions and boil for another minute. Serve separately with a bowl of rice, or serve it over the rice in a bowl.
Notes
Kimchi kongnamul guk keeps well in the fridge for 3 to 4 days. If frozen, the texture of soybean sprouts may get stringy or tough.