The number one cause of bad washer smells is the growth of bacteria or mold inside the appliance. You may not see it but those spores are multiplying behind the scenes! Add some vinegar and baking soda to your washer and run a wash cycle. This will help clean out the cause of the smell. To prevent your washer from stinking, you should use minimal fabric softener and run regular cleaning cycles with vinegar and baking soda.