Maybe rubbing alcohol? It’s a solvent. Ideally you’d want to pull the battery etc. while doing this and try to tip it so the coffee gets diluted by the alcohol and then carried out as the solution drips off. I’ve seen Linus clean other computer parts with alcohol baths. I’d try something like 70-90%. I might just be talking out my ass though. But that’s what I would try if I was determined to try to fix it without taking it apart. :p Make sure it has time to dry before using it.
I love mr. robot :)