Spray Lysol or Ozium in it. I prefer Ozium since Lysol is sort of strong. You can find the Ozium at any car parts store or car wash. It's very effective against odors. Another option is F'breeze. The only problem with F'breeze is that the smell is masked, not elimated as with the previous two. Another thing I do is keep an air freshner in my helmet. Like the ones you hang from your mirrors. I prefer cherry. It sounds cheesy 'til you try it.