In Jainism, during Upvas (fasting), the general rule is that no food or water is to be consumed for the entire duration of the fast, which is typically from sunrise to the next sunrise (a full day). Drinking water is not permitted during Upvas.

For Tivihar Upvas (also known as Tivihar Tap), the rules are slightly relaxed compared to complete Upvas. In Tivihar, one refrains from eating any food, but drinking boiled water is allowed. However, the boiled water can only be consumed during daylight hours—from sunrise until sunset. After sunset, no water or any liquid is to be taken.

Summary:

• During Tivihar Upvas, you may drink only boiled water.
• Boiled water must be prepared fresh and can be consumed only between sunrise and sunset.
• After sunset, you should not drink any water until the next sunrise.

Always consult your local Jain Sangh or spiritual teacher for guidance, as practices may vary slightly among different Jain sects.