Last time, in addition to water, we (i did the fast alongside and with guidance from a "healer"), added various small amounts of juice to the water, including ginger juice, a local green green leaf (chaya i think it was called) and radish. Also added to the water was 2 tablespoons of honey per day as we were fairly active. Also included daily meditation, yoga, sun-gazing and reading material from gurus.
Next time (assuming i pluck up the courage to do it) i guess it will be similar. i would also use MMS (chlorine dioxide) now i am aware of it and experienced in it's use for even deeper cleansing. Ideally i would also do so in a completely dark space (so obviously no sun-gazing :-), and in silence, so i will need someone to support me.
i intend to create a dark room in a cellar under my house for that purpose and to offer that as an additional option for retreat guests.