immediately wipe inside of cube then wash all pieces + core then unscrew all screws, wipe all water off screws then wipe rest surfaces of cube. Even do this if it is stickered, those can be replaced. Just try to save your gts2.
I would either soak it in water for a bit, or clean and scrub every piece for a long time, using a cloth and a toothbrush. Speedcubereview's video where he put some kind of hand cream in his cube and had to clean it out may help.