Breakdown of Они пьют всё, кроме алкоголя.
они
they
пить
to drink
весь
all, the whole, everything, everyone (весь, вся, всё, все)
кроме
except
Questions & Answers about Они пьют всё, кроме алкоголя.
Why does алкоголь change to алкоголя here?
The preposition кроме (except/besides) always requires the Genitive case. Because алкоголь is a masculine noun ending in a soft sign (-ь), you drop the soft sign and add -я to form the Genitive.
Can кроме also mean 'besides' or 'in addition to'?
Yes! Depending on the context, кроме can mean 'except' (excluding something) or 'besides' (adding something). Here, the contrast with всё (everything) makes it clear that it means 'except'. If the sentence was Кроме алкоголя, они пьют сок, it would mean 'Besides alcohol, they drink juice'.
Why use всё instead of все?
The word всё means 'everything' (a neuter singular pronoun, used for concepts and inanimate things). The word все means 'everyone' or 'all' (a plural pronoun used for people or groups of countable objects). Since they drink 'everything', we use всё.
What is the infinitive of пьют, and why is there a soft sign inside it?
The infinitive is пить (to drink). It has an irregular present tense conjugation that inserts a soft sign into the stem to separate the consonant from the vowel ending. The forms are я пью, ты пьёшь, он/она пьёт, мы пьём, вы пьёте, они пьют.