Even rubber watchbands absorb odor... Metal is your best bet; get an ultrasonic cleaner, that'll take care of all your crevice problems.
As an avid g shock collector I bought a vintage g shock (OG dw5000; the one that started it all) off of eBay and it reeked of rotten meat despite being very clean and in good condition. It was cleaned often as indicated by the seller but rubber becomes pourous as you wash them more and there was surface wear resulting from all the washing on this specific one. I ended up keeping it in activated charcoal to get rid of the smell. Flipside is the original 30+ year old rubber on it is still pliable and soft due to that fact.