In the Instant Pot, combine the kimchi, onion, mushrooms, garlic, ginger, sesame oil, soy sauce, gochugaru, sugar, salt, and water.
Secure the lid on the pot. Close the pressure-release valve. Select MANUAL/PRESSURE COOK and set the pot at HIGH pressure for 3 minutes. At the end of the cooking time, allow the pot to sit undisturbed for 10 minutes, then quick-release any remaining pressure.