First wash the bottle with sand and water. Then dry it under the sun. And when it will dry & come in natural temperature then take it to ur room. And fill the bottle with water. But make sure the full bottle is pour but upper 2 inches should blank. And then wait. And measure temperature in every 10 minutes. Within 1 hour what is the maximum temp? Count it. If it is more than 106 then you can sell. And it has handsome amount.

And there is some fraud parties who say the bottle which is heated under the sun can also be sold. Dont trust them. Coz these bottle can be made by any1.....best of luck