How the hell did you get syrup inside the controller? You are going to have to open it up and use loads of rubbing alcohol. The longer you leave it like that, the stickier it's going to get.
It wasn't me it was my brother lol and he had the controller on the bed next the the plate of pancakes which was also sitting on the bed and when he went to get back on the bed the plate tilted over. I had a silicone case on it so the outside was fine but syrup got between the sticks