It seems no matter how hard you try, microwaves are difficult to keep clean. Just one overheating of soup and the entire inside is caked with baked-in tomato. Thankfully, according to tips site Cozi, you can heat a wet sponge or rag to steam the inside and clean it easily.Heating a wet sponge is also a good way to disinfect it. They recommend heating the sponge or rag for three to five minutes, then let it sit for a few more to let the steam loosen up the grime. After that, you should be able to wipe your microwave clean.