Bud Light lost 0.9 percentage points of the total market share in the United States in the most recent quarter, while Budweiser lost 0.35 percentage points.

The mega brands have struggled to win over American millennials.

Younger drinkers are increasingly ditching beer, instead preferring wine and spirits.

Budweiser and Bud Light's battle to win over Americans continues.

Bud Light lost 0.9 percentage points of the total market share in the United States in the most recent quarter, parent company AB InBev reported on Thursday. Budweiser lost 0.35 percentage points in the same period.

"We must stabilize the share segment performance of our mainstream brands, such as Budweiser and Bud Light, as mainstream lagers are the entry point for the beer category, and as such play a meaningful role in delivering our strategy," AB InBev CEO Carlos Brito said in a call with analysts on Thursday.

Beer consumption among drinkers from 21 to 24 has fallen roughly 3% per year over the last 15 years. Beer penetration fell one percentage point in the US market from 2016 to 2017, while both wine and spirits were unmoved, according to Nielsen data. And, per-capita consumption of beer in the US dropped by nearly 10% from 2008 to 2017, according to Euromonitor data.

Millennials, especially, are more likely to prefer spirits and wine than older generations. And, when they do drink beer, they are drinking more craft beer — meaning that mega brands like Bud Light and Budweiser are being hit especially hard.

Budweiser, once the best-selling beer in America, was knocked off the list of the three best-selling brands tracked by Beer Marketer's Insights last year, for the first time since the 1970s. According to UBS data, millennials were less likely to recommend Budweiser than the general population.

While AB InBev is anxious to reinvigorate its Budweiser and Bud Light brands, executives are also looking to new variations and types of beverages to grow sales. According to the company, Bud Light Orange and Budweiser Reserve were "among the top share gainers in the US this year" despite their parent brands' struggles.

AB InBev reported that US revenue grew by 1.5% in the third quarter. The company reported a profit of $956 million, down from $2.06 billion during the same period a year earlier.