Plastic water bottles are a divisive issue for many consumers, but not for Sarah Kauss.

The defining moment happened at Kauss' five-year business school reunion in 2009.

"A professor did a presentation about the global water crisis and the impact on the planet from plastic waste," said Kauss. "I knew then that my bottle idea had to happen."

Before then, Kauss would carry other metal water bottles with her but wasn't happy with their look.

In 2010, Kauss launched her startup S'well, a line of insulated reusable stainless steel bottles that are designed to keep drinks cold for 24 hours and hot for 12 hours.

Since then, the New York-based firm has sold 4 million bottles. The business is profitable and saw revenue surge 400% between 2013 and 2014 -- hitting $10 million last year. "We expect revenue to grow exponentially again this year," she said.