A smelly microwave isn't a pleasant one, but whether you've been heating up spicy food or managed to burn something in there, there are ways to fix it. If you've followed the above methods to clean the inside, your microwave is likely smelling better already.
But if it's just a smell you need to deal with, start by airing out your microwave by leaving the door open. Then add a small bowl of baking soda to your microwave when you shut the door. This will absorb the bad smells. For extra potency, add a few drops of lemon juice.
You could also try microwaving a small bowl of 2 tbsp white vinegar and 1 cup of water for a couple of minutes. Then let the microwave air out. The vinegar will absorb the bad smells.