(It's similar to Uber or Lyft, but eco-friendly — and free. (Pictured: Founders Alex Esposito and James Mirras.)The Free Ride)

Growing up in the Hamptons, Alex Esposito and James Mirras knew one thing to be true: The beach was great, but the parking sucked.

Between the crowds and the permit-required parking lots, there was rarely an easy — or cheap — way to enjoy a summer day on the sand.

In 2009, Esposito and Mirras, now both 30, finished their undergraduate studies at the University of Florida and Bentley University, respectively. They toyed with the idea of starting a shuttle bus company as a solution to their childhood grievance.

But there were vehicle costs, like insurance, maintenance, and fuel, to consider. Plus, the two were eager to begin their professional lives; Mirras was off to work at Morgan Stanley and Esposito was pursuing his MBA at Bentley.

"We ended up putting the idea on the back burner," Esposito told Business Insider. That is, until a few years later when a discussion about using freebies as a tool to sell products came up in one of Esposito's business school classes.

"So, Starbucks gives away internet to sell coffee, Gillette gives away razors to sell blades. James and I kind of scratched our heads and said, well, what if we made our beach bus free?" Esposito told Business Insider. "We decided to put together this model where, if electric cars can cut out the cost of fuel, and if advertisers can pay to sponsor the service, then we can provide a totally free service for this one-to-two mile gap."

They ran with the idea — but kept at their day jobs — and founded the Free Ride in the summer of 2011, debuting with a few open-air, fully electric cars operating in East Hampton. Riders could either hail a shuttle from the app, or wave one down on the street for a ride to the beach or a local restaurant. The next summer, the network expanded to include routes in Montauk and Southampton.

In a crowded summer destination like the Hamptons, Esposito and Mirras found companies were willing to pay big for innovative and interactive advertising. Big enough, in fact, that it covers operating costs, and riders don't have to pay a dime.

By the following summer, Mirras had left Morgan Stanley to run operations for the Free Ride full-time. They added additional routes in South Florida and Santa Monica, California, and were soon partnering with household brands like JetBlue, Corona, Coco-Cola, and, later, L'Oreal. Since then, ad revenues have surpassed seven-figures, nearly doubling every year, according to Esposito.