Fasting in Islam means not putting anything in any orifice of the body.
You can read about the film's various sex scenes and orifice exploration right here.
They can corrode through whatever human tissue they contact if swallowed or stuck into an orifice, sometimes in a matter of hours.
orifice or·i·fice (ôr'ə-fĭs)
An opening, especially to a cavity or passage of the body; a mouth or vent.