As changing drinking habits meet a desire to cut calories, hard seltzer, a genre of alcoholic sparkling water made by fermenting sugar, is growing at a precipitous rate across the US, unleashing a raft of fan art and causing suppliers headaches.

According to Nielsen, the measurement firm, hard seltzers have seen a year on year sales growth of 193%, spurred by a combination of low calories and broad flavour choices. In comparison, for some of America’s biggest holidays, beer sales showed just 0.1% growth in the beer segment. Hard seltzer’s growth is only outpaced by hard kombucha. Both beverages have a beer-like typical ABV of 5%.

Despite accounting for just 2% of the beer market, the demand for hard seltzers, and its most popular brand White Claw, owned by the same private company as Mike’s Hard Lemonade and which enjoys 50% of the market, has left bars and grocery stores struggling to maintain supply, the Guardian reported.

White Claw’s advantage over beer is clear at the calorie level. While a 12-oz can of Heineken beer has 142 calories and contains 11g of carbs, White Claw clocks in at just 100 calories and 2g of carbs.

Craft brewers have noticed the trend and are trying to muscle in on the action. As beer volume sales grow, hard seltzers offer a new avenue to reach beyond the craft beer consumer. “We’re not really targeting the guy drinking session I.P.A.s,” one brewery president told the New York Times.

Analysts expect the category to continue its strong growth. UBS analyst Sean King, speaking to Markets Insider, says that the $550m category could, by 2021, be worth $2.5 billion in the US alone – an annual growth rate of 66%.

Despite White Claw’s dominance in the market – somewhat reminiscent of the vaping brand Juul’s internet-fuelled fame – big beer players have also got involved in the category. In 2016, Anheuser-Busch bought a three-year-old brand, SpikedSeltzer, which was since renamed to Bon & Viv’s Spiked Seltzer.

Ultimately, analysts point to the product’s tapping into a broader movement. “It’s hitting on a major trend, which is health and wellness,” explained Caroline Levy, an analyst at Macquarie Group, speaking to Fortune. Though it’s share of the total market remains small, the interest comes from “how incredibly it’s growing,” she added. “The sales cycle for hard seltzer was originally seasonal and in the last year or so, it’s had tremendous growth over the winter.”

Sourced from Nielsen, The Guardian, New York Times, Markets Insider, WARC, Fortune