Ms. Zhao orders from Splendid Spoon in Williamsburg, Brooklyn, which offers vegan, gluten-free soups in single-day cleanses, with the option of adding five hearty soups as meal replacements over the course of a week. Around three-quarters of its clientele — predominantly women — choose the longer version, according to Nicole Chaszar, the company founder. Sales, she said, have tripled annually since the line was introduced in 2013.

In January, Soupure, a company that opened in Los Angeles in 2014, expanded from local delivery to shipping its cleanses nationally. It also operates a popular outpost in Brentwood Town Center there. In Philadelphia, Real Food Works, a meal delivery service, added a soup cleanse to its menu in late 2013.

The appeal of souping, in part, is that it promises an easier detox than a juice cleanse.

“When you do juice cleanses, your blood sugar can spike really high,” said Despina Hyde, a registered dietitian at NYU Langone Medical Center. “Soup cleanses are inherently lower in sugar over all because they’re using more vegetables and complex carbohydrates versus fruit. They also tend to be higher in fiber, which has so many good benefits.”

Elina Fuhrman, who founded Soupelina in Los Angeles in 2013, chimed in similarly: “The juice cleansing trend started from a good place and evolved into something that’s not so healthy, because there’s a lot of sugar and not enough nutrients that the body needs.”

Soupelina offers soup cleanses of different durations as well as single-serving soups, and business has doubled in the last 12 months, Ms. Fuhrman said. The soups are prepared mostly with produce from two local farmers’ markets; the colorfully named offerings include Kale-lifornia Dreamin’, Lentil Me Entertain You!, and And the Beet Goes On, a borschtlike crimson concoction.