Short answer: Yes, many people do drink water on the last day of Samvatsari (Paryushan), but whether you should or not depends on the vrata you are observing.

• Samvatsari is the forgiveness day, marked by Pratikraman and seeking forgiveness (micchami dukkadam).
• There is no universal rule across all Jain traditions that forbids drinking water on the last day. For most families, water is allowed and they continue with daily needs or the usual end-of-fast practices.
• Some practitioners, especially if they are keeping a strict fast (upvas) on Samvatsari, may choose to abstain from food and drink for part or all of the day. In such cases, they would follow the specific vow given by their guru or temple tradition.
• Digambar and Shwetambar communities sometimes have slightly different customs about fasting duration and rules, so if you are following a particular tradition, check with your local guru or temple for the exact guidance.

If you tell me which tradition you follow (Digambar or Shwetambar) and what vrata you’re observing, I can give a more precise, tradition-specific answer.