Carl DeSantis was a few years removed from his big payday—the $1.8 billion sale of Rexall Sundown, the publicly traded nutritional vitamin company he founded—when his longtime business partner, Jim Steinhauser, brought him his first six-pack of a new sugar-free energy drink called Celsius about 15 years ago. DeSantis trusted his instinctual eye for a good product and thought he’d stumbled upon a winner when he tasted the drink, which was made by a small mom-and-pop outfit then based in Delray Beach, Florida, where he lives.

Not many people agreed with him over the next decade. DeSantis was the largest investor in Celsius Holdings when it went public for the first time in 2008, but after just three money-losing years, it was delisted from the Nasdaq with the stock tanking. DeSantis kept investing millions for marketing and advertising, and it took its second try at the public markets in 2017. The stock finally took off in 2020, soaring tenfold.

Celsius’ flavors include names like strawberry guava and peach vibe, and it’s now on shelves in 82,000 stores, marketed as a healthy option free of preservatives with a formula of vitamins and minerals that keeps consumers energized and boosts metabolism. DeSantis’ 31% stake in the company is worth $1.2 billion.

“We call it a 12-year overnight success story,” says Jeff Perlman, executive vice president at DeSantis’ family office, CDS International Holdings. “He from the very beginning saw the potential of the brand and never wavered in the conviction that given enough time and enough resources and smart investment, that it would catch on.”

DeSantis, 81, had the patience and the ability to stay committed to Celsius thanks to his entrepreneurial success, which began at a young age. When he was 13, he started breeding parakeets in his garage, printing out makeshift ads at school and inserting them into copies of the Miami Herald he delivered on his daily route. He claims he profited about $30 a week and cashed out for $400 after six months, when he got tired of caring for the birds.

He started working at Walgreens as a stock boy while he was a student at Florida State, then dropped out and took a job at a store closer to home in Miami. He got an opportunity to be a store manager in Greensboro, N.C., in 1962, but moved back to Miami after a few years to manage a Kroger-affiliated Super X drugstore.

By 1976, DeSantis felt that the sunscreen products the drugstore sold were inadequate and thought he could do better. He and the pharmacist at the store invested a total of $5,000 to start a sunscreen business as a side hustle, and soon expanded to offer vitamins by mail too after customers at the store would badger him for cheaper options.

His three children and his wife’s friends from church helped him pack orders in the beginning, and when he was passed over for a district manager job at Super X, he quit to devote himself to Sundown Vitamins full-time. It was generating $20 million in annual revenue by 1985, when he bought the Rexall trademark, adding national name recognition from the brand that once had 25,000 drugstores across the nation but had fallen to the brink of bankruptcy.

He recruited famed TV personality Dick Clark to be a spokesperson for the business, which he took public in 1993, and appeared on Forbes’ Best Small Companies list several times in the 1990s. In 2000, he cashed out when former Dutch food giant Royal Numico bought Rexall Sundown for $1.8 billion. DeSantis owned a third of the business, and his two sons Dean and Damon, who worked for him, owned an additional 17%.

With his newfound cash pile, DeSantis set up a family office in Boca Raton, Florida, and diversified his investments, including local real estate and restaurants, a 50,000-acre ecotourism reserve that he developed in South Africa and sold in 2012, the Tabanero hot sauce brand and his own necktie collection. None caught his attention quite like Celsius, which was founded in 2004 and started selling its drinks a year later.

“This goes hand in hand with what I was doing,” DeSantis says. “It fits in with a healthy lifestyle, and that’ll never go out of style.”

He invested early, and extended Celsius a $3 million line of credit to fuel an advertising campaign in 2010, but it didn’t get the business off the ground. After it was delisted, he recruited a new CEO and management team to orchestrate a turnaround.

“Carl stated when I first started, the goal for me joining the company was, number one, to get the company profitable,” says John Fieldly, who joined Celsius as its CFO in 2012 and has been its CEO since 2017. “And number two, get the company back listed on Nasdaq to make all the investors whole that invested initially.”

A team of Celsius investors and executives visited famed marketing guru Jack Trout and decided its positioning was lacking muster. They were trying to market Celsius as a weight loss product, but pivoted to an overall energy message to help people get through a workout or their work day without sugar and jitters.

“We came out of that day with the fitness play, the ‘Live Fit’ mantra,” Perlman says. “Once we got the marketing muscle behind that, which was an additional investment by Carl, that seemed to resonate.”

Celsius rang the Nasdaq bell on June 6, 2017, completing phase one of its comeback—though the stock didn’t move much for years and was 25% below its IPO price last March 16, closing at $3.16. Since then, shares have skyrocketed, peaking at nearly $70 in January before settling back around $50. Revenue grew 74% in 2020 to $131 million, with $8.5 million in net profit, and investors are still expecting extraordinary growth: Shares are trading at almost 500 times annual sales. Hong Kong billionaire Li Ka-shing is another believer, owning a 12% stake in Celsius that makes up a small slice of his $32.6 billion fortune.

Celsius, now headquartered in Boca Raton, is sold mostly in convenience stores as well as some big names like Target and Walmart, and Fieldly says it’s the third-largest energy drink seller on Amazon, closing in on Red Bull. Amazon accounts for about 15% of Celsius’ revenue.

DeSantis sold about $25 million in stock during its rise last year, but continues to advise Celsius executives and says he’s committed to keeping the lion’s share of his stake invested for the long haul. At age 81, he even muses about starting a new vitamin business catering to boomers concerned about longevity. True retirement is still far from his mind.

“Some people collect cars,” Fieldly says. “That’s not his M.O.—Carl collects businesses.”