Apple cider vinegar has always worked for me. :)
Oh, while I'm at it, apple cider vinegar will clean a dirty microwave like a dream! I found this out yesterday. We can't use household cleaners or chemicals because we have birds, but since ACV does well in the washing machine, I sprayed some on the stubborn, greasy built-up gunk in the microwave. About 20 minutes later, the gunk was "liquified", and literally wiped off with a paper towel. No scrubbing needed whatsoever! :thumbup: