Cut rice cakes, fish cake, and scallions into bite-size pieces.
Add water, gochujang (Korean chili paste), red pepper powder, soy sauce, and sugar to a pot and bring to a boil.
Once boiling, add the rice cakes and fish cake, and simmer on medium heat for 5 minutes.
Add scallions and continue cooking for 2 more minutes so the flavors combine.
Taste and adjust seasoning, then transfer to a serving plate.