Your shoes are breeding ground for bacteria. If not sanitized and cleaned properly and timely, the fast multiplying bacteria can get their condition worst. To blast the bacteria in your shoes, use rubbing alcohol (Isopropyl Alcohol). Ensure that you do a spot test first. These are best at killing bacteria and offing the fungi. As you do this, give them 30 minutes to air-dry to get them back to normal conditions. These hacks work well in any conditions!