What is Brewskis?
1.
Beers. More than one beer.
He's going to pick up a 12 pack of brewskis later.
See
2.
What you call multiple beers if a) you're cluelessly still living in the 1980's; b) ironically pretending you're in an 80's teenage T&A film to underline that your life experience completely revolves around what you have watched on television.
If a) then cut that mullet. If b) no-one thinks you're cool, so stop it. Stop it right now.
"Dude... totally rad kegger. Pass the brewskis. Cowabunga! Is that Gary and Wyatt? Let's kick their butts!"
See