Answer

In Ekāśanā, you may drink water only during your one sitting for food, according to the discipline you have taken.

After you finish that one sitting and get up, you generally do not drink water again until the vow period is over.

Explanation

Ekāśanā means eating one time, in one sitting. Traditionally:

• You sit once for food.
• You take your meal within that sitting.
• Water is also taken within that same sitting if permitted.
• Once you get up, the eating/drinking period is considered complete.

If your question is about the next day, then water can usually be taken after the Ekāśanā vow period ends, depending on the exact rule followed in your family, sect, or by your guru.

Spiritual Understanding

The purpose of Ekāśanā is self-control, simplicity, and reducing attachment to taste and bodily comfort. So water is also kept within discipline, not taken freely throughout the day.

Takeaway

For Ekāśanā, drink water during the single sitting itself. After getting up, do not drink again unless your guru or family tradition has given a specific allowance.