I dropped a small drop of hand sanitiser in between my option and command keycaps. HELP!

Hard to tell, except there are gaps between keycap faces, & part of functional design.

Key switches and other parts, including silicon damp-proof layers, are under keycaps.

And if you were not using the portable Mac, to have turned-off macbook,

& set it upside-down and let it cool; would have been better, of course..

A 'service appointment' will likely be required to assess condition & estimate cost.

• Apple Repair and Repair Status Check - Official Apple Support

https://support.apple.com/repair

• Get your Mac ready for service - Apple Support

https://support.apple.com/en-us/HT209095

• Apple - Find Locations (usually will show nearer AASP/Apple choices)

https://locate.apple.com/

I don't think this would be too detrimental.

Hand sanitizer is a naturally thick substance so as long as you wiped a majority of it off initially you should be good. depending on the substance it may also be alcohol based. If that's the case it shouldn't be a matter to worry about, alcohol typically goes well with tech.

If you happen to have a wired keyboard (with USB-C/3.1 Adapter?) that may allow use for awhile.

Alcohol-based sanitizer with other additives, would be difficult to clean from there, as you guess.

An external keyboard may buy time, if you had one already set to use. A warm computer could

let the sanitizer thin ~ and then soak further, into the top section of bottom case. [I feel your pain!]

Hopefully you can locate another computer to complete the tasks; it might fail.

Maybe someone else has workable solution?

Sorry! 🙀|🦁🐯🐻|🤔

I thought I might also add, if you are truly worried about burning the circuitry underneath the caps, I'd recommend you turn off your device and keep it off for a while just to allow any residue to dry to minimize the chance of a short circuit occurring.