Cut rice cakes and fish cakes into bite-sized pieces.
Slice the onion and green onion.
Pour water into a pot and add gochujang (Korean chili paste), gochugaru (chili powder), sugar, soy sauce, and minced garlic to make the sauce.
When the sauce starts to boil, add the rice cakes, fish cakes, and onion. Simmer over medium heat.
Once the rice cakes become soft, add the green onion and simmer once more.
Serve in a bowl to finish.