Drink nothing? Impossible! (2,2)
I believe the answer is:
no go
'impossible' is the definition.
(I've seen this before)
'drink nothing?' is the wordplay.
'drink' becomes 'nog' (nog is a kind of drink).
'nothing?' becomes 'O' (O resembles 0).
'nog'+'o'='NO-GO'
(Other definitions for no go that I've seen before include "Futile" , "in vain" , "Area you shouldn't enter" , "report on person lacking energy?" , "Impossible" .)