Like in the other question, Italian (unlike English) uses double negatives. Mai is used with non to say "they never drink beer. Where I personally am confused is if one takes out the mai, will it still bean the same thing? Here's a link for double negatives: http://italian.about.com/library/fare/blfare141a.htm
They do not drink beer ever was marked wrong and said it should be they do not ever drink beer. Really?
Ellos nunca beben cerveza . Ellos "they" means Loro? I have that doubt i cant understand why is "they"