This video shows how to wash a horse's sheath. The instructor notes that you do not want to wash the horse's sheath to often because certain good bacteria needs to exist in the horse's sheath. It is noted that you can use soap but his method of choice is to just use water to clean the sheath. This sort of sheath cleaning is only necessary with tame horses and must be done very carefully. The instructor notes that you can just let water run into the sheath and just let it remove any dirt. It is noted that you need to know the horse well and be very careful when approaching the horse before cleaning a sheath.