In the middle of a harsh Indian summer, when temperatures climb past 45°C and access to cool drinking water becomes more necessity than comfort, a simple cloth bag is quietly drawing attention online for doing what most people now rely on refrigerators for.

Priced at around Rs 300, the portable cooling bag works without electricity, batteries, or any modern machinery. All it needs is air, water, and time.

Its principle is remarkably simple. The bag is made using a porous fabric that retains moisture. When water is poured over it, the outer surface stays damp. As that water slowly evaporates, it pulls heat away from the contents inside, naturally lowering the temperature. The........

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