BEVERLY HILLS, Calif. — An annual charity party here was in full swing, but its host, Rohan Oza, was late. He was cruising toward Los Angeles aboard a private jet with Rick Yorn, who manages the pop star Justin Timberlake, and Ben Weiss, the founder of Bai, a maker of low-calorie soft drinks.

Mr. Oza, 45, an early investor in Bai, had just helped persuade the Dr Pepper Snapple Group to buy the company for $1.7 billion. The deal created a windfall for him, Mr. Weiss and Mr. Timberlake, whom Mr. Oza had persuaded to invest in and endorse the brand. (“Five calories, naturally sweetened and tastes amazing — what’s not to love?” Mr. Timberlake said in an interview.)

When Mr. Oza finally arrived at the Children Matter, an event he hosted at his home with Gene Simmons, the Kiss bassist, he was understandably ebullient. Guests who had paid $2,500 a ticket were mingling with famous people, watching Mr. Simmons perform classics like “Rock And Roll All Nite.”

They sipped cocktails mixed with Bai and Wtrmln Wtr, another of Mr. Oza’s investments. While he talked Bollywood-themed parties with the actress Kristen Wiig, he showed off a refrigerator full of beverages from companies he had backed. Mariel Hemingway watched him point out bottles of Health-Ade Kombucha. He pressed a bottle of Wtrmln Wtr into the hands of Ms. Wiig’s companion. He clutched a bottle himself as he stood for photo ops, his shiny black hair rising like the swirl of a kewpie doll.

“I believe in living my brands, not marketing them,” Mr. Oza said, offering a can of Bai Bubbles. “I’m not selling Bugattis. These products have got to be fun and engaging and desirable.”

He stopped midthought to high-five the singer Ne-Yo, who immediately brought up the Dr Pepper deal. “You owe me one, man,” he said. “I’m in.”

Movie stars, singers and athletes have long profited from product endorsements, but A-list names tended to stick with high-end luxury products and giant brands like Coca-Cola (LeBron James, Penélope Cruz) and Pepsi (both Cindy Crawford and, back in the day, Joan Crawford). They were usually just “spokesmodels” or “brand ambassadors.”

But thanks in part to Mr. Oza, famous actors, musicians and sports stars now lend not just clout to little-known soft drinks, snacks and more, but financial and creative involvement. Mr. Timberlake, for example, is taking the position of chief flavor officer with Bai “to have a little bit of fun with my title and to show people this isn’t your typical endorsement deal,” he said. “It’s a partnership.”

Mr. Oza was the marketing head at a small beverage company called Glacéau and had the idea to make a deal with Curtis Jackson, known professionally as the rapper 50 Cent, to promote the company’s Vitaminwater in exchange for a stake in the company instead of cash. Mr. Jackson made an estimated $50 million to $100 million when Coca-Cola bought Glacéau for $4.1 billion in 2007.

By contrast, Glacéau later cut a more traditional deal with the football star Tom Brady, reportedly paying him up to $5 million for a three-year contract to promote its Smartwater drink.

Mr. Oza left Glacéau after the sale and has since become a go-to broker between small companies and big celebrities. Through his connections, Jennifer Aniston invested in Smartwater, Rihanna and Madonna invested in Vita Coco, and Beyoncé invested in Wtrmln Wtr.

A year ago, Mr. Oza started the investment firm CAVU Venture Partners with Clayton Christopher, the founder of Sweet Leaf Tea, and Brett Thomas, a former hedge fund investor, so they could use outside money to invest in products.

Some celebrities are going beyond investing in a company to creating one, like Jessica Alba and her household products business, Honest Company, and Kate Hudson with her fashion brand, Fabletics, which is owned by the TechStyle Fashion group.

And the film studio STX Entertainment has paid stars less than what is typical and made up for it with a bigger share of the film’s overall profits, essentially incentivizing them to use their power to make a hit. “Anyone can smack their name on a drink brand, but it’s more beneficial to that star if they can help own and build and incubate a project,” said Sophie Watts, the president of STX.

This realization has helped solidify Mr. Oza’s wealth, though his is not a Horatio Alger tale.

Sitting by his pool on a quiet afternoon, over a snack of Chef’s Cut beef jerky (which he stores in bulk in the garage), Mr. Oza described how he was born in Zambia to a wealthy Indian family, attending the English prep school Harrow, the University of Nottingham and the University of Michigan business school. He developed a love of dancing and golf. He was on the varsity bowling team. “It’s the footwear,” he said. Today he was wearing Louboutin loafers with his T-shirt and jeans.

After business school, Mr. Oza got a marketing job at Coke. His work there earned him awards, but some executives wanted him out. “Rohan was an anomaly at Coke, not the blue blazer and khaki pants, but he was also a magical figure who captured people’s attention in ways that many other corporate folks couldn’t,” said Jeff Rubenstein, who worked with Mr. Oza at Coke, and is the chief marketing officer at Wtrmln Wtr.

Sensing trouble, Mr. Oza left for Vitaminwater, a fledgling Queens-based brand. “One of my best friends at Coke said, ‘Good luck with that,’” he said.

That friend can now visit Mr. Oza not just at the palatial house here but at a luxury apartment in TriBeCa and a house in the Hamptons not far from Shinnecock Hills Golf Club, where the “brandmaster,” as some call him, has played with Mr. Timberlake.

He met Bai’s Mr. Weiss through the former Senator Bill Bradley, who was also thinking about investing. His caddie introduced Mr. Oza to the makers of his favorite beef jerky, and he has helped turn that business into Chef’s Cut.

At a recent “vision session” with Bulletproof Coffee, he grilled the founder Dave Asprey and his fellow investors Trinity Ventures about the company’s hiring plans and e-commerce strategy.

Mr. Oza had questions about one product in particular, FATwater, which is basically water that is full of coconut oil fats. Mr. Asprey extolled fat’s health benefits, then Mr. Oza tactfully noted that drinking fat could be a tough conceptual leap for most consumers. In the end, he suggested that Mr. Asprey do something about the taste.

“I take his message, which he says is rooted in conventional wisdom, with a grain of salt,” Mr. Asprey said. “Taste is very important to Rohan. It’s just far less important for me than how it makes you feel.” But Mr. Asprey agreed that pushing too many new products onto store shelves could backfire and that it may be better to build excitement for FATwater by first selling it online to die-hard fans.

Mr. Oza is certain that with the right marketing and product development (and perhaps, the right support from a famous person), Bulletproof Coffee will follow in the footsteps of Bai, Vitaminwater, Smartwater and Vita Coco. “People don’t want soda anymore,” he said. “This is a movement.”

But the movement doesn’t take itself too seriously. At Mr. Oza’s Diwali party in October, he wore a shimmering silver designer kurta. The former supermodel Tyra Banks chatted about her start-ups with Anjula Acharia, an investor at Trinity. Tommy Lee, formerly of Mötley Crüe, was also there. The guests eventually held a dance-off, boys against girls.

Mr. Oza’s team won.