Answer

In Jain ekasana, water is generally taken only during the permitted daytime period and according to the specific rule you have accepted for your tapasya.

If you are observing the common rule of ekasana with boiled water, then you may drink water during the allowed daytime hours, but not after sunset.

Explanation

In Jain practice:

• Ekasana means eating only once in one sitting during the day.
• Water rules can vary depending on the vow taken, family tradition, sect, and guidance of one’s guru.
• Many Jains drink only ukāḷelu pāṇī — boiled and cooled water — during tapasya.
• Water is generally avoided after sunset.

So the exact time depends on your local sunrise and sunset, and the specific niyam you are following.

Spiritual Understanding

The purpose of ekasana is not only food restriction, but also self-control, simplicity, and reducing attachment to taste and bodily comfort.

Takeaway

You may have water during the permitted daytime period according to your accepted niyam, preferably boiled water, and avoid water after sunset. For exact timing today, follow your local Jain calendar, temple announcement, or guru’s guidance.