Well it's as clear as crystal. It isn't the coffee, it's the bunk. If you don't sleep at night it isn't the coffee that keeps you awake, it's the bunk.
9 seconds sound clip from the Christmas in July (1944) classic radio play.
You can hear this line at 00:06:32 in the radio play.
Quote context
[...]
- Well that's what makes it such a cinch this time!
- Can't you just see it over there on Broadway? A great big electric sign...
- You gotta' admit, that's some slogan!
- Uh huh!
- Well do you get the point? Do you understand what it means?
- Yes...
- I know what it says, I just don't understand it.
- Well, a kid of two could understand it.
- Now that's simple enough, isn't it? Coffee makes you sleep!
- Well, he says it makes you sleep. He's a Viennese doctor.
- Coffee keeps you awake. That's a well known fact! Why are you so pig headed about it?
[...]