In Jainism there isn’t a formal, canonical ritual specifically for “making holy water.” Purity and holiness come from intention, conduct, and reverence, not from a special magical rite performed on the water itself.

A simple, authentic approach you can follow is:

• Prepare a clean, pure vessel and water that is free from contamination.
• While you pour or hold the water, recite a short, appropriate Jain devotion or mantra (for example the Navkar Mantra or a short prayer for ahimsa and spiritual upliftment).
• Use the water with a mindful, respectful attitude—often as an offering to a tirthankar symbol, or as part of a devotional practice—without attributing magical power to the water itself.
• Maintain ethical conduct (non-violence, truthfulness, cleanliness, restraint) in the process, since holiness in Jain Dharma is primarily about inner purity and right conduct.

If you need, I can share a simple Sanskrit/Prakrit phrasing that aligns with Jain devotion to accompany this practice.