This posts shows how to clean the inside of a microwave the easy way – simply use vinegar and water! This is the best way to clean a microwave with natural ingredients.
Fill a microwave-safe bowl (no special tools needed!) with about 1/2 cup of vinegar and 1/2 cup water. Set your microwave for around 6 minutes – you want to give the vinegar mixture plenty of time to boil and let off steam. The steam is the key to my how to clean a microwave with vinegar tutorial. Once the microwave stops, don't open the door for an additional 5 minutes or so (again, to give that steam lots of time to break up dirt and grime).
Now, wipe! Get all of the steam off of the inside surfaces of the microwave. You can very carefully get a little bit of the cleaning liquid on your rag/sponge to clean it needed – just make sure it isn't too hot first. I wipe down all of the interior surfaces of the microwave with the damp cloth as well as the inside of the microwave door, giving any gunk or splatters a little bit of extra elbow grease. You can also use this mixture on the outside of the microwave – vinegar is great for streak-free cleaning!