Jeannette Luoh used to be a devoted soda drinker. The former real-estate lawyer would down one to two cans of Coca-Cola or Pepsi a day. But about five years ago, she noticed that she could no longer finish a 12-ounce can.

“So instead of buying regular sizes, I would buy the mini-Cokes, but it was still too sweet,” said the 42-year-old from Taipei, Taiwan. “I realized my tastes had changed gradually and I didn’t enjoy [soda] anymore.”

When Steve Hersh, her then-fiance, proposed making and marketing a less sweet soda, one aimed more at adults, she thought it was a great idea. In 2003, the couple, now married, created GuS – short for Grown-up Soda.

The two-year-old business isn’t going to challenge Coca-Cola’s or Pepsi’s bottom line anytime soon. But it has grown quickly – so quickly that Ms. Luoh was able to leave her legal job in April 2004 to help Mr. Hersh expand the brand.

Today, GuS – available in flavors of dry Meyer lemon, star ruby grapefruit, extra dry ginger ale, dry Valencia orange, and dry crimson grape – is sold in grocery stores such as Whole Foods, in specialty gourmet shops like Zabar’s, and in restaurants like Per Se and French Laundry.

The couple just landed a Harry and David account and will be in 150 of the company’s stores nationwide.

A sixth flavor is coming in about three weeks: dry cranberry lime.

Inspiration sprang from unemployment. When the Internet startup Mr. Hersh worked for collapsed in 2001, the five-year veteran of the consumer packaged-goods business sought to return to the industry. After nine months of searching, he only landed one job interview. Frustrated and at loose ends, Mr. Hersh revived a childhood interest of selling his own food product.

“I always said I wanted to do Steve’s Salsa or Hot Sauce,” said the youngest child of a father who owns a small import-export business and a retired social worker mother. “When I was about 7, I went around the neighborhood selling chocolate bars I made from the Willy Wonka chocolate bar kit I had gotten as a gift.”

In between planning a wedding with Ms. Luoh and overseeing the purchase of a new apartment for the two of them, Mr. Hersh kicked around the idea of buying into a business and bounced ideas off Ms. Luoh.

He was intrigued as much by Ms. Luoh’s growing distaste for traditional soda as by his father, who would cut his Coke with seltzer to blunt the sweetness.

Plus, Mr. Hersh had some experience with the beverage industry. After four years on Wall Street, he became interested in marketing and packaged goods while attending Kellogg Business School. He trained for a year at Procter & Gamble, then returned to New York in 1995 to work for Cadbury Schweppes’s A&W Root Beer.

The idea coalesced in March of 2003. By April, the couple incorporated the company, Utmost Brands, and decided to launch four of the 11 flavors they had concocted in their home kitchen. One month later, they came up with the name GuS as well as lined up a bottler, a flavor house, and a design team. They worked feverishly with the aim to make the June 30 Fancy Food Show at the Javits Center.

The flavor house and the designer “did a great job,” recalled Mr. Hersh. “The second the flavor house called, I got in my car. I brought them down and checked them with friends. We had a poker game right when we were developing, and the guys I have poker with, I had them try it. … It seems like heresy, given my business background, but our feeling was, we’re not trying to appeal to everyone. We wanted our friends and families, people in their 20s to 30s, to think it tastes great.”

A day before the show, Mr. Hersh convinced two local stores to carry GuS. Then, at the show, Zabar’s and Los Angeles’s Surfas Restaurant Supply and Gourmet Food placed orders. By October 2004, Mr. Hersh was handling about 50 accounts in New York City alone, personally delivering orders out of the trunk of his Subaru Outback.

The only complaint from customers was that high fructose corn syrup was an ingredient rather than cane sugar. So that fall, they stopped the bottling and went back to their flavor house to reconfigure the formula using cane sugar. It was a risky – not to mention expensive – decision, but it proved worth it.

Not only did the sodas go from 95 calories a bottle down to 90 calories, GuS finally landed Whole Foods, which refuses carry products if they have ingredients on its no-no list. High fructose corn syrup is one.

Whole Foods tried GuS in the Columbus Circle store. It was there that they caught the attention of Per Se’s sommelier. He liked the product so much that he pairs GuS with dishes for diners who don’t want wine or spirits.

Throughout, Ms. Luoh continued to practice real-estate law at her Manhattan firm. But the two had a goal: Make the business enough of a success so she could leave the law firm.

“Steve needed someone to work with him,” Ms. Luoh said. “I was at the point where I felt I had enough of law. I was waiting for a way out, but I couldn’t quit without a job. This was the perfect opportunity.

“I was working longer hours, and Steve was having all the fun,” she added. “We started talking about wouldn’t it be great [if] we worked together. At the end of April, the timing was right and mentally, I was so ready to leave.”

Despite the seemingly overnight success, they still take a hands-on approach to the business. They drive up to Massachusetts every other month to deliver the fruit juices, labels, and packaging to the bottler. They personally oversee the production run, donning hairnets and jumping into the assembly line.

When they’re not at the bottler, the two are on the road, doing demos at stores like Whole Foods. To maximize time and effort, Ms. Luoh works one store while Mr. Hersh drives to another.

“We’re big on quality, not quantity,” said Mr. Hersh. “We are not out to blast the whole country as soon as possible. We’ve turned away a lot of sales and accounts that might not be best for us. We don’t want to erode what we have by trying to be everywhere.”

Meanwhile, the newlyweds are enjoying working together.

“A thing I appreciate about this whole adventure is that we’re having fun doing it,” said Ms. Luoh. “I think that’s important.”