To say that someone "can't drink fog" is to say they're a lightweight at drinking.
It's history comes from many a Kerry man who has emerged from a pub after many pints, is suddenly hit by the air and immediately feels more drunk
Perhaps because of certain distinct physical differences between male and female, this term has been used to describe abilities that are more common in the male sex. Such abilities include; map reading, spatial awareness, computer programming, DIY, and mathematical ability.