The tl;dr of events:

• Dude was gifted some cases of beer from his boss.
• Took a swig from a can, and died a few days later.
• Turns out boss was part of international drug ring.
• They got the cans mixed with legit cans of beer, they would process the ones with meth and give away the rest.
• Boss accidentally gave away one of the meth cans

Slightly more info:

• He gave a can to his buddy at the same time, buddy's can was fine. He tasted the tainted can and spit the sip out right away.

• The boss had a warehouse with a bunch of cans where they'd process the drugs and such. They had footage of him there which is how they caught him and figured things out.

There's a lot more to the whole thing, but he didn't just buy laced beer from the store... if that makes things any better/worse