Samantha Durfey was a high school sophomore in St. George, Utah, when the first Swig soda shop opened its doors there. Today, at 28, Ms. Durfey, visits the shop at least three times a week. She usually orders a Save Me Jade — Diet Dr Pepper with sugar-free vanilla and coconut flavor syrups — but every now and then she’ll change her order if she wants a break from caffeine.

“They have really good carbonated-water drinks, and because carbonated water itself is disgusting they mix it with fresh fruits and sugar-free syrups and stuff,” she said, “and it makes it taste really yummy.”

Since the first Swig opened in 2010, dozens of soda-shop chains and independent soda shacks have opened from Idaho to Utah to Arizona, an area of the Mountain West sometimes called the Mormon Corridor. A significant portion of the region’s population belongs to the Church of Jesus Christ of Latter-day Saints, and the church’s prohibition on tea and coffee has spurred a niche beverage market that has intensified in the last decade, hitting a fever pitch during the pandemic.

New soda shops are also increasingly opening in other parts of the country, including South Carolina, Florida, Texas and Oklahoma.

“Some people say, ‘Oh well, it’s just a Utah trend,’ and we kind of proved that wrong when we went to Oklahoma, and proved people like their soda everywhere,” said Nicole Tanner, who founded Swig with her husband, Todd. “It may sound so weird to some people who have never been, but it’s happiness in a cup. I’ve always known from the start that this is something that can and should go everywhere.”

The idea for Swig came out of Ms. Tanner’s family outings to Sonic, where “they had the good pebble ice, and the good foam cup,” she said.

Several of the major soda-shop chains in Utah — Swig, Sodalicious, Fiiz and others — are projecting aggressive growth in the next few years. Kevin Auernig, an owner of Sodalicious, said the 25-shop company will double its locations in the next three years. Fiiz started franchising five months after opening in 2014, and now has nearly 40 stores in Utah, Texas, Colorado, Idaho and Nevada, “with a bunch more in the hopper,” said the chain’s owner, Jason Anderson. There are 26 Twisted Sugar shops around the country, but by this time next year there could be nearly 100 franchises, said Tonia Jardine, an owner of the chain.

Swig, which employs about 700 people, plans to open 10 to 15 shops a year, and in two or three years, Ms. Tanner said she hopes there will be 200 or more shops across the United States.

The soda-shop chains pay special attention to the history of Starbucks — which decades ago expanded at a breakneck pace, from fewer than 20 stores in 1987 to more than 100 in 1992. Worldwide, there are more than 30,000 Starbucks today. Many soda-shop owners believe their industry could be at least that successful.

“There is a great soda-drinking culture in the Mountain West region,” Mr. Auernig said, adding, “What Starbucks originally did for coffee was kind of our idea with soda.”

Soda consumption in the United States has been steadily declining over the last two decades, but Americans still drink an annual average of 37 gallons of soda per person, according to 2019 data from the Beverage Marketing Corporation.

Soda-shop offerings vary from store to store, but they always include brand-name soda or energy-drink bases, with add-ins, like flavored syrups, fruit purées and dairy products like creamer and half-and-half. At Fiiz — which opened in 2014 north of Salt Lake City in Bountiful, Utah — a menu of nearly 600 drinks, using 67 different syrups, gives customers vast drink options.

After Mitt Romney was photographed drinking a Diet Coke while running for president in 2012, the church posted a statement on its website clarifying its stance on caffeine, saying it “does not prohibit the use of caffeine.” The Word of Wisdom, the church’s health code, specifically bans hot caffeinated drinks, like coffee and tea.

Brant Ellsworth, an associate professor at Central Penn College in Summerdale, Pa., specializes in the history of the church. He said that its clarification about caffeine did not likely spur the popularity of soda shops in Utah. Dr. Ellsworth, who grew up in the church and went to Brigham Young University, said his mother “religiously drank Coke” and his father “religiously drank Diet Coke.”

“I know that Mormons need to get their caffeine fix, and with coffee and tea being off the table, Dr Pepper can be the go-to staple,” he said.

Dr. Ellsworth, who wrote a chapter in the 2020 book “This is the Plate: Utah Food Traditions,” said soda shops “really are tongue-in-cheek with the way they engage with L.D.S. culture, its history and some of its practices” — pointing to drink names like the Second Wife at Sodalicious and the Missionary at Swig.

Ms. Durfey said the church’s clarification on caffeine has given many mothers, in particular, the freedom to indulge. Women make up a large majority of soda-shop customers, especially mothers who grab a drink between dropping off and picking up children from school.

“Moms can’t function without caffeinated beverages,” said Ms. Durfey, a mother of two.

“We’re exhausted,” she said. “I don’t know a single mom who cannot go through the day without some form of caffeine. I think that has definitely aided in the popularity of soda shops, because L.D.S. women can’t have coffee, they can’t drink alcohol. So their vice of getting that relaxation, that energy, and that whole kind of ritual I guess you could say — I feel like soda is their only option.”

The shops have also become popular with high school and college students for dates and hangouts, acting as a bar or coffee-shop substitute for people who do not drink coffee or alcohol.

Judy Levin, who wrote the recent book “Soda and Fizzy Drinks: A Global History,” said the shops hark back to the temperance-era soda kiosks and fountains in Europe and North America, which “were absolutely set up as an alternative to the bar.”

“To the extent that I was willing to do predictions in the middle of Covid, I sort of felt the soda fountain might come back for various reasons, because of the social function that it once had,” Ms. Levin said.

While the pandemic halted or shuttered many restaurants and bars, soda shops were able to stay open and thrive during the first few months of the pandemic, largely because of their drive-through lanes.

“It became a nice little escape from being stuck at home all the time,” Ms. Durfey said.

As a nod to her hometown, Atlanta, Olivia Diaz, who is 27 and lives in Orem, Utah, likes to order Life’s a Peach — Dr Pepper with peach and vanilla syrup flavorings, and half-and-half to make it “extra dirty.” (The term “dirty” refers to the flavor add-ins, and its use in marketing was the basis of a 2015 trademark lawsuit, when Swig sued Sodalicious.)

Ms. Diaz started going to the soda shop once or twice a week after her sister began working at one. Now, she goes only a couple of times a month. “I just realized that probably drinking that much soda probably wasn’t the best for me,” she said.

Many of the dirty sodas, which come in sizes up to 44 ounces, can contain up to 1,000 calories.

Rebecca Fronberg, a program manager at the Utah Department of Health, said that “it’s not really great to drink our calories” and that sugar in the diet “is always a concern for diabetes, heart disease and all kinds of things.”

Despite that, many seek out soda as a pick-me-up, a small indulgence.

In Clinton, Utah, Nichole Richins, 42, lives within 10 minutes of 10 different soda shops. Her usual order is a Polar Punch from Swig, a blended energy drink with blackberry, raspberry, strawberry, ginger ale and vanilla cream. She visits the shop about once a week, “but if it’s a hard week, it will be more.”

“That’s my extra treat,” she said.

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