Sales of the products were "significantly ahead of what we thought it would be to the point where we ran out of supply," Starbucks CEO Laxman Narasimhan told investors on Tuesday.

"And I think that it wasn't a supply issue necessarily, but it was more the demand was ahead of what we thought it would be," he continued. "We had to pull back marketing, and my sense is that as you look at what we now have in our stores, they're back in stores with new products, and it's a platform that we will continue to build over time."

Narasimhan said the pearls had the highest launch-week sales at the company. The pearls contributed to overall sales of Starbucks' Refreshers drinks reaching an all-time high during the quarter.

Many customers have been adding the pearls to other Refreshers beyond those included in the core pearls lineup, two baristas told Business Insider.

"We go through them pretty fast," one Starbucks barista in Cape Cod, Massachusetts, told BI of the pearls. The barista's employment has been verified by BI, but they requested anonymity to protect their employment.

Customers "definitely like" the pearls lineup, the employee said.

Boba, also known as bubble tea, is a Taiwanese drink that's served cold and typically made with milk, tea, and chewy tapioca pearls.

The drink is a booming business in the US, especially among Gen Alpha and Gen Z consumers. Dedicated boba stores offer a huge variety of flavors and toppings, like fruit, grass or coconut jelly, red beans, brown sugar, and pudding.

Starbucks has never described its drinks as boba, simply calling them beverages "with pearls." Rather than the traditional chewy tapioca, Starbucks makes its drinks with popping pearls — also popular at boba chains — and none of the beverages on Starbucks' set pearls lineup appear to contain tea.

"It's not real boba," the Massachusetts barista said. They added: "The people who like real boba probably wouldn't like it as much."

The success of Starbucks' pearls comes as the chain continues betting on cold drinks, which made up 76% of its beverage sales in the quarter. This includes the chain's new iced energy drinks, which launched in late June.

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