I had a few Ouzo's in Suva once and the next morning I felt terrible. However, after careful scientific analysis I noted that since I had felt fine when I went to my bunk, but diabolical when I got out of it, it wasn't the Ouzo that did it, but the sleep.
There have been a number of occasions since when I've noted the same thing with various beverages.
It's the sleep that does it.