The 'Saturday Night Fever' actor was shocked but amused when his son, Benjamin, started shooting apple juice, like it was an alcoholic drink, when they were relaxing in his home bar.
During an appearance on 'The Late Show with David Letterman', he said: "We were in the pool room which has a bar and he said, 'Get me a drink dad,' and I said, 'OK.' So I poured him a little apple juice and he said, 'Down the hatch!' He said, 'Cheers" and he said, 'One for the road!'
"I said, 'Where did you learn that?' I figure it was 'Popeye' or one of the cartoons. He's so energetic, he's a little jock, he loves to run around. He loves to play sports, we play ball, we swim. A lot of pretending."
The 59-year-old actor - who also has 13-year-old daughter Ella Bleu with wife Kelly Preston - also spoke with the host about his famed airstrip at home, which he can fly his private jet up to and park right outside his house.
He added: "I still live there, there's only a few of us on the airport. The other day I flew in to [New York for the show] and I said to my wife, 'Honey I gotta go do 'The Letterman Show'.' And I zipped off."
When David then asked him whether he needed a car, John replied: "Not really. It's a lot of fun.
"When I was a kid I had a vision of this life and how I've established it. You know, dreams sometimes come true."