Srutakirti: Srila Prabhupada sat in a window seat near the back of the airplane. Shyamasundar and I were seated next to him. As was the custom on the transcontinental flights, the flight attendants frequently offered refreshments to passengers to avoid the dehydrating effects of recycled air.
"What is that?" Srila Prabhupada asked me as she approached our seats.
"Oh, that's 7-Up, Srila Prabhupada," I said. "Would you like some?"
"Yes. Let me try it," he replied.
I immediately requested three cups for all of us. Shyamasundara and I waited for Srila Prabhupada to take the first sip. We wanted to be certain the 7-Up would be prasadam. He drank some and put the cup down on the table. "Ah! This is very refreshing," he said. We finished our drinks within minutes.
During that flight, we had 7-Up three or four times. Each time Srila Prabhupada drank one he said, "Ah, very refreshing. This is very good." One time the flight attendant put the can down on the table along with the cups filled with ice. Srila Prabhupada picked up the can and asked, "What are the ingredients?"
"Water, sugar, citric acid, natural lemon-lime oil," he read. "Oh! This is all right. This is very good. It is all natural ingredients."
Srila Prabhupada was marvelous. He was very enthusiastic about his discovery. I excitedly watched him enjoy each moment.
Reference:What is the Difficulty? - Srutakirti Dasa