Twenty two years ago, I bought a second hand solar powered Casio scientific calculator from a colleague. It was filthy, ewwwww, so I carefully washed the surface using a soft cloth, over a sink full of hot soapy water, then accidentally dropped it in the sink.

I took it out, rinsed it thoroughly in clean warm water then left it to dry on the radiator overnight. The next morning it was very dry and worked fine. It lives in my briefcase and still works fine.

Clean water will not damage most commercial and industrial electronic equipment, nor will soapy water provided it's not powered up at the time and you rinse all the residue off and let it dry thoroughly before applying power.

Oh, remember to take any batteries out first.