Answer

During Upavas, if you are observing the common rule of taking only boiled water, then you should generally not take Gandhodak after Pooja.

Explanation

In Jain practice, Gandhodak is the sacred water used in Pooja, often containing sandalwood, saffron, or other fragrant substances. Because it is not simply plain boiled water, taking it may break the strictness of an Upavas where only boiled water is allowed.

If your Upavas rule is:

• Nirjala Upavas — no water at all, so Gandhodak should not be taken.
• Boiled-water Upavas — only boiled water within permitted time, so Gandhodak should generally be avoided.
• Chauvihar Upavas — no food or water after sunset, so nothing should be taken after that time.

Spiritual Understanding

Upavas is meant to increase self-discipline, purity, and detachment from taste and comfort. Even though Gandhodak is sacred, during tapasya one should follow the vow taken with care and avoid anything outside the rule of the fast.

Takeaway

If you are doing Upavas with only boiled water, it is best to take Gandhodak respectfully on the forehead rather than drink it. For your exact family or sect practice, follow the guidance of your Guru Maharaj, Sadhviji, or local Jain Sangh.