Unpleasant shoe odour is caused by the bacteria in your shoes. By killing those odour producing bacteria you can easily eliminate the bad smell from your shoes.
To do just that, add a teabag in each shoe and leave it there for 1 to 2 hours. Teabags effectively kill bacteria and thus eliminates the smell. You can use any type of teabag. Black teabags are the most effective as they contain a high concentration of Tannin which is good at killing these odour producing bacteria.
Once the odour is gone, wipe the inside of shoes and let it air dry. Your shoes will be smelling fresh as new!