Meat says many things in interviews .. probably to keep himself from falling asleep
.. but lager is hardly "beer"
However, some of his shows have had him simulating drinking from a can or bottle as part of the act .. a good case in point was the show in Newcastle where he chose to use a bottle of Newcastle brown (because he tends to try and do things which pay some recognition to the area or city he is in) and then when his vocal chords froze was accused by some of drinking on stage so "he couldn't have been ill" .. it's called acting!
Personally I take Scott Ian's writing with the same pinch of salt I take many things, and what a person does now can be very different to what they did on one described incident over 15 years ago at a time they were under stress
Meat would say now he doesn't smoke, and he hates smoking .. but when he was younger he did, and smoked cigars for many years. Not now.
If you want to know Greg, there's only one person who can answer your question .. but does it really matter?