In Jain upwas (fasting), you still need to keep the body hydrated and comfortable while your palate and meals are restrained. Drinking hot water is common for a few practical reasons:

• Digestion and comfort: Warm or hot water can be gentler on the stomach when solids are avoided or reduced, helping with digestion and reducing abdominal discomfort.
• Hydration: Even during upwas, you need to stay hydrated. Warm water is pleasant and may encourage more regular sipping.
• Cleanliness and purification vibes: In many households, water is boiled or warmed as a precaution to keep it pure and easy on the system during austerities.

Notes on tradition:

• In different Jain communities (Digambar vs. Shwetambar), practices can vary in detail, but both traditions typically emphasize restraint, cleanliness, and self-discipline during upwas. If you’re following a specific vrata or guru’s guidance, align with those instructions.
• The key aim of upwas is restraint and purification, not hardship. Warm water is a practical aid that supports those goals when it’s allowed within your scriptural or guru-guided rules.

If you want, I can look up more precise references from Jain scriptures or authoritative JainKnowledge pages to clarify how hot water is treated in your specific tradition.