In Jainism, the "Kalpvriksh Tap" (also known as Kalpvriksha Tap) is a type of austerity (tap) inspired by the mythical wish-fulfilling tree, Kalpavriksha, mentioned in Jain scriptures. The specifics of Kalpvriksh Tap can vary according to different traditions and sects, but typically, it is a form of progressive fasting or regulated food intake.

In this tap, the practitioner gradually reduces the number of food items consumed each day, often for a set period of time (such as 16 days). On the first day, one might eat a certain number of food items, and each subsequent day, the number of items is reduced, ultimately reaching only water or complete fasting.

Regarding eating food or drinking water:

• Yes, during the initial days of Kalpvriksh Tap, you can eat food and drink water, but the number and type of food items are restricted and systematically reduced as the days progress.
• In the final stages, the practitioner may end up consuming only water, or may even observe complete fasting, depending on their capacity and the specific tradition followed.

The main purpose of this tap is to cultivate detachment from tastes and material pleasures, develop self-control, and purify the mind and body.

It is always advised to undertake such austerities under the guidance of an experienced Jain monk, nun, or knowledgeable layperson.