During the month of Ramadan, most Sufis go on a fast from sun up until sun down.  It is a dry fast.  And that means no water as well as no food for the whole day.  For Sufis, this would be considered studying the cleansings of the body as related to preparation for strength in the physical as well as the mental.  Apparently these teachings and practices come in the form of fasting, meditation (dzikr), and prayer (salaat); practices meant to purify one's body, thoughts, and actions.  Yeshua (Jesus) was also said to have studied in Benares (a Holy Hindu city) where he learned  these teachings combined with other teachings.