A lot of folks who cycle like beer too. Or maybe a lot of folks like beer, and some people who do, cycle too. In Japan they have athlete sized beer. Little cans (135ml -about 1 dollar) that amount to a couple mouths full, and slightly larger cans (250ml).
The beer section is mostly single cans, and the 6 packs are a rip off (pictured at about 11 dollars). So it's kinda like the beer aisle is saying, "go ahead, drink some beer, but just one." Ideally, the way to drink beer in Japan is to go someplace. The tap beer is so good, it's always in a frozen glass, and there's usually a deal. So to compare, a single can at a store will cost you around 300yen(~3 dollars), while at an Izakaya (bar sort of place) or Ramen shop, it will be someplace around 200-400yen (~2-4 dollars) on average, and you've got some atmosphere.
Although there is a lot of size variety, there is very little taste variety readily available. The big 3 makers that most people know, Asahi, Sapporo, and Kirin rule. Suntory also makes great beer and has as strong a presence as the others, but somehow is not as well known overseas. But among these big 4 makers there really is no taste variety. It'd be like going to the store in the US and seeing Bud, Michelob, Miller, and Coors. Microbreweries are around, but they've yet to get their product out, even to major metro areas. I have seen one small brewery's beer, in Kamakura - it's pictured.
Many have heard of Beer vending machines in Japan. They do exist, but you need an ID card to operate the machine, and as far as I have tried, a foreigner ID card doesn't work. So you need to be Japanese, or pissed off enough to destroy the machine. The cops don't have guns and they ride bikes normally, so it's not a mismatch anyway.
As far as drinking the beer, well, you can just drink it. It doesn't really matter where you are. Nobody will give you any troubles. Walking on the street, at the platform of the train, sitting in the park - just about anyplace is fine. It is against the law to ride a bicycle intoxicated - as it probably is anywhere - but here, people get caught for it and the penalties are stiff. Another reason to get the athlete sized beer.