A microwave is a kitchen appliance that many can forget to clean, and this tends to build up bacteria and strong smells, however, cleaning depends on the frequency of use.
Cleaning it at least once a week or after use can help keep the bacteria away while still maintaining its efficiency.
Studies have shown that both E. coli and Salmonella can survive inside the microwave.
This study claimed that microwaves can be microbial hotspots. Not only is the inside of the microwave risky, but also poses a risk in public/general areas.
To remove smells in both your microwave and fridge, baking soda is a really good ingredient. Just place an open bowl of baking soda in the fridge or microwave and let it sit there for 24 to 72 hrs. Easy as that.