Scottish - Fuckbast is the word Buckfast transposed. Central region slang for the popular tonic wine brand 'Buckfast'.
A commonly held belief is that the number embossed on a Buckfast bottle denotes the sweetness of the contents. This is merely a batch number and is not an indication of the quality or sucrose level of the contents.
Right ya fanny, my bottles got a 2 on it so it's the sweetest Fuckbast ever man. Let's go to the park and sit on the swings. Aye man Falkirk Fear! Let's stamp some authority!