And the method is easy:
1. Take a cotton wool ball.
2. Soak it well with isopropyl alcohol.
3. Clean your sandals or flip-flops with the soaked cotton ball.
4. Let the shoes dry completely before wearing them again.
That’s it.
Most of the other methods people are recommending may help in preventing the odor but only alcohol truly does kill the bacteria and keep your sandals stink-free (for a while).
Notes about this method
Make Sure that both your feet are and the sandals are fully dry before putting them back on.
If you don’t, the moist will probably make your efforts worthless by allowing the bacteria set in, and you may also harm the materials on the footbed.
Also, beware that if you have a cut or a wound on your feet the contact with isopropyl alcohol might sting when you first put the shoes back on. Let the sandals enough time to air out after the treatment. Wipe the dry sandals with a dry paper towel to remove some of the excess substance. And use a band-aid when needed.