Help! My roommate put chicken stock in my rice cooker
You can try heating some vinegar to near boiling and pour into the coil area.
Slosh it around and pour it out.
Repeat if needed and make sure to let it dry completely before using it again.
If the rice or whatever burnt into the bowl, cleaning it is iffy. You can try the hot vinegar there also, but then let it soak for a couple of hours. Then scrubbing lightly with a rough sponge.
This is a case where I'd see what a good stiff brush with soap could do. If it doesn't work on the rice cookwer, use it on the roommate.
Your biggest need is to remove all grease - everything else is either burnt on or soluble. And if the grease and solubles are gone, maybe you can live with what remains, even if it's burnt on.
But it sounds like the roommate didn't let it boil dry, so maybe you can save it - mightn't be pretty but possibly will be functional.
But let it dry several days before trying to use again.
I can so relate to this. Last month, my DH put a box of Rice A Roni in our rice cooker :O I came home from work to find the vent spewing bits of dried herbs. It was a mess, needless to say. He still to this day doesn't understand why that was a bad thing to do. He bought us a new one. Thankfully the one he destroyed was from Costco so it was only around $40, but still . . .