I spilt my coffee accidentally and it entered my violin through the f-hole.
Will my violin's sound change?
What should I do?
My violin is a beginner violin.
May depend whether it was black/white coffee, with/out sugar. And how much. Not much black will most likely dry up and maybe leave a stain inside, but not affect anything else. Add milk and sugar, and I'd try to remove those with a damp or wet cloth carefully through the F-holes. Then dry naturally - not on a heat source.
Maybe the question is not what should I do, but what should I do in the future? Keep it in its case, and certainly away from anything likely to get spilled! (And children...)
If your "beginner violin" starts to get smelly, or you can see mould growing inside it, the cheapest option would probably be to just throw it away and buy another one. You can keep all the removable parts like tuning pegs, strings, tailpiece, etc as spares, if the coffee missed them!
It's not worth the cost of getting a very cheap instrument cleaned professionally, and trying to do it yourself isn't likely to be a success.
How much coffee are you talking about? Obviously try to get as much of it out as you can.
It will still be playable, but I'd leave it out to dry. Be careful poking around in there, or you could knock down the soundpost, which you'd have a pay a bit to get reset. (You know to never take all the strings off at one time?)
I don't think one accidental spill will do any great deal of damage, so long as you let it dry out as much as possible. Aka I can't see it warping and splitting. Again, you just have to hope there's no mold that develops from sugars ect. I know with electronics they say to leave it in rice, but with a violin, I'm not so sure I'd recommend that. I'd worry a grain would stick to half dry coffee, and mold. Just leave it out for a few days to dry.
Well, it may be too late for that, but since you are asking about "waterproof", I'd guess about black tea, possibly with sugar.
For better or worse, what you can't shake/tilt out again, you want to spread thin by turning the instrument back and forth and up and down. It will likely stain the vignette that way but that's better than if you just let the coffee/liquid collect in one corner or line. This is wood: a little moistness once and spread out will not impress it. But the violin is glued shut at its lining using bone glue. Water, particularly hot water, will start to unset the glue. And sugar will interfere with its consistency then.
Depending on what you mean with "beginner violin", you may have some industrial wood glue inside instead (or whatever can be used for saving cost). In that case staining the vignette beyond readability might increase the value of the violin, and the coffee will not cause noticeable harm either way.