With a strategy that combines both disruptive and conventional routes, Coca Cola India has turned Thums Up and Sprite into billion-dollar brands, and is now trying to bring Maaza into the same club.

But thanks to the mania for green stocks, the company’s market value has soared 800% in recent months to reach $5.6 billion. It’s not alone. Since November, a wave of once-obscure clean-energy ...