"There are two reasons for that," the chairman and CEO of Berkshire Hathaway said in a "Squawk Box" interview. "One is people seem a little bit more willing to experiment with different diets and food than they were five or 10 years ago."
"There's a huge loyalty factor, but it's not as strong as it was," he added.
Secondly, Buffett cited a longtime struggle between retailers and consumer packaged goods companies. He mentioned when Costco, one of the nation's largest wholesale clubs, dropped Coca-Cola over its prices in 2009.
Coke was able to survive that, Buffett said. "If Costco decided to drop a bunch of other brands," the packaged goods company might feel it more than the retailer, Buffett said from Omaha, Nebraska, where Berkshire held a weekend of events around Saturday's annual meeting.
Buffett and his longtime investing partner and vice chairman, Charlie Munger, spoke to the tens of thousands attendees on a wide range of topics from their massive stake in Apple to missing out on Google and Amazon to bashing bitcoin as "rat poison."
Coke and its rival Pepsi have struggled with weakening sales of their sugary sodas. Still, Coke last month reported quarterly earnings and revenue that beat Wall Street's expectations as a relaunch of its classic Diet Coke drink and expansion of new brands helped drive sales.
With Berkshire's 2018 annual meeting in the books, users can revisit the highlights in CNBC's Warren Buffett Archive, which houses searchable video from 25 full annual meetings, going back to 1994, synchronized to 2600 pages of transcripts. The Warren Buffett Archive also includes 500 shorter-form videos arranged by topic, CNBC interviews, a Buffett Timeline, and a Berkshire Portfolio Tracker.