Some spiritual disciplines have a concept of a "water fast" (see https://en.wikipedia.org/wiki/Water_fasting), during which one consumes only water, tea w/o sugar, etc.
Clearly, consuming even water is prohibited on standard Jewish fast days. However, does Jewish law possess any concept of a water fast, such as for a penance, personal fast day, etc? I'm aware of the custom of refraining from food but not liquids before visiting the kever of a tzadik, so I'm curious if this applies elsewhere. Thanks!