Answer

If you are doing a Jain upvas today, you may start drinking water after completing the upvas according to your tradition, usually after sunrise the next morning, and typically after doing Pachchakkhan / taking permission to break the fast.

Explanation

In Jain practice, upvas generally means abstaining from food for the day, and in many traditions it also includes restrictions on water depending on the type of upvas:

• Chauvihar Upvas: No food or water after sunset until the fast is properly completed the next day.
• Tivihar Upvas: Water may be allowed during permitted daytime hours, but not after sunset.
• Upvas with boiled water: Some people drink only boiled water during allowed hours, as per their vow.

So the exact time depends on what Pachchakkhan you took and what your family/guru tradition follows.

Spiritual Understanding

In Jain Dharma, fasting is not only about avoiding food. It is a practice of self-control, awareness, purification, and reducing attachment to the body. Therefore, the fast should be completed respectfully and according to the vow taken.

Takeaway

If you took Chauvihar Upvas, drink water only after sunrise tomorrow after properly completing the fast. If you took Tivihar, water may be allowed during the day before sunset. For certainty, follow the Pachchakkhan you took or ask your guruji/elders.