New Delhi, Nov. 2 -- Billionaire hedge fund manager Bill Ackman has long considered Warren Buffett his "great professor" in the business of investing. But even for a close associate like him, Buffett's extreme brand loyalty caught him completely off guard.

Speaking on a recent episode of the Equity Mates Investing podcast, Pershing Square founder Ackman recounted hosting Buffett for dinner at his home "years ago".

Ackman, anticipating his guest's well-known preferences, stocked up on Cherry Coke, but politely offered still or sparkling water to start. Buffett declined and asked for a Coke.

"But I said, you know, 'Don't you drink water?'" Ackman recalled on the podcast. "And he said, 'Bill, I haven't had water in 48 years.'"

But this i...