Don't let a smelly vacuum cleaner undo your otherwise fine work. Try to notice if your vac is emitting a foul odor. Some have even described it as smelling like vomit. This can result from moisture building up in your vac's bag or plastic dust container. As the suction air travels through this damp mess, it picks up a nasty odor and spreads it throughout your customer's premises. If your vac has a paper bag, remove it and replace immediately with a clean one, and the odor should stop. If it has a cloth bag, empty it, then - at your first opportunity - thoroughly wash the bag out.
With a plastic dust cup, empty immediately, and the smell should stop. If after doing the above, you are still getting bad smells, it is probably due to a build-up of damp crud within the air channels of your vac. If so, I would take the vac to my local vac shop and find out if they can clean it up for you. If this would cost more than a new vac, then get a new vac.
That actually happend to me on a job the vacuum was ommiting a very bad dog smell luckily I had a second vaccum.
What I did was to R/R the bag like mentioned and I also used a product similar to odorcide on the hepa filter I actually soaked the filter with this and vacuum and the smell was not only gone but the room smelled great from the air going through the filter.