Cut the rice paper into quarters.
Slice the fish cake and onion into bite-sized pieces.
Add water, gochujang, gochugaru, soy sauce, minced garlic, and sugar to a pan and bring the sauce to a boil.
When the sauce boils, add the fish cake and onion, and boil for 2 more minutes.
Add the rice paper and stir well, cooking for 2–3 minutes.
Add green onion and mix once more.