Odo-ban, Sink-the-stink, MiraZyme... Listerine... all work... anti-bacteria and odor stuff combined is what you're looking for...
Fill up tub or small Rubbermaid bin, stick a weight in each boot so it remains completely covered... soak overnite... remove boots from tub or bin... *DO NOT* rinse...
Drip dry for several hours in a space with solid airflow... *DO NOT* wring... if you're really worried you can do a spin in the washing machine... SPIN cycle *only*... to get water out... still let air out for a couple hours though...
Here's the magic... if you don't have a boot drier or something like that... stuff with *newspapers*... yes, *newspapers*... stuff full... if it's something like a 5mm zippered boot, you'll use 3 or 4 full sheets of newspaper... don't crumple up too tight but full sheet of newspaper should take up a size between a baseball and a softball... stuff full... change newspaper every hour until it's basically dry... then let air out a bit more without newspaper...