Author Laura Newcomer suggests: “Pour some vinegar into a small cup and mix in a little lemon juice (exact amounts don’t really matter). Put the cup in the microwave, let the microwave run for 2 minutes, and leave the door closed for several more minutes. Finally, open the door and simply wipe down all the sides with a warm cloth or sponge—no scrubbing required!”
Laura Newcomer, March 29, 2015. “27 chemical free recipes for DIY spring cleaning,” Greatist.com.