Smelly (in a bad way) vacuum?

what I have done is remove the plastic container and wash it, dry it out and then let it sit for awhile to kinda "air dry", You might want to change your filters in the vacuum and if all else fails spray with febreeze.

If you have a small place and it takes a long time to fill a bag, then I know you hate to change the bag before you have to.they are expensive these days. If you have a pet , then pet dander that you vacuum up can be the culprit, just expect this. If it is just common dirt you might try something call Carpet Fresh. This is a fragrant powder that you sprinkle on your carpet then vacuum up. It leaves not only your vacuum bag but also your whole house with a clean sent Be sure to use only a small amount though, excess powder left in the carpet will seep through into the pad over the years.

Crickets & spiders don't cause bad smells

If it has a bag then change it.

If it's a plastic canister then remove it, empty it and wash it.

well, first off change bag if ithas one, second, if it does have a bg, you can throw a fab. soft. sheet in it.