In Jainism, practices like raatri bhojan tyag (avoiding food and sometimes water at night) are encouraged for lay followers (shravaks and shravikas) as a form of self-discipline and to minimize himsa (violence to micro-organisms that are more prevalent at night).

Ekasana (eating once a day), biyasana (eating twice a day), and raat ka posh (not eating or drinking after sunset or a specific time at night) are all recommended practices, but the level of observance can vary depending on one’s spiritual capacity and vow level.

Drinking water at night: According to Jain scriptures and traditions, drinking water at night (after sunset or after a designated time, like 10 pm) is discouraged because the increase in microorganisms in water after dark leads to greater himsa when consumed. Ideally, boiled water (that has cooled) should be consumed, and only during the day.

If you do not do ekasana or biyasana: Even if you are not observing ekasana or biyasana, the principle of avoiding water and food at night (raat ka posh) still applies as a separate vrata (vow or discipline). The practice of not drinking water at night is not conditional upon practicing ekasana or biyasana. It is a separate recommendation to reduce violence and for spiritual discipline.

Summary:

• According to Jain conduct, you should avoid drinking water after sunset or after the time designated for raat ka posh, regardless of whether you do ekasana or biyasana.
• Boiled and cooled water, if absolutely necessary, may be consumed during the day.
• Strict observance may vary according to one’s capacity and guidance of your Jain guru or tradition.

If you are considering these practices, it is best to consult with your local Jain leader or guru for practical guidance according to your situation.