In Jainism, abstaining from water (and all food) for one full day is called Nirjal Upvaas (निर्जल उपवास) during Paryushan. "Nirjal" means "without water" and "Upvaas" means "fasting." So, Nirjal Upvaas refers to a fast where the person does not consume either food or water for the entire day, from sunrise to sunrise (or sometimes sunrise to the next sunrise, depending on tradition).

This form of fasting is considered highly austere and is observed by some devout Jains during Paryushan as a means of self-purification and penance.