This is one of the current brewing and bottling facilities for Sapporo beer. Guided tours are led (in Japanese only) by very enthusiastic brand ambassadors past windows that allow visitors to peer into the high-tech factory. You need to make reservations by 5pm the day before (best get a Japanese-speaker to do this). Note that the facility is not in operation every day; when you reserve be sure to ask. Non-drivers get two free beers at the end!
Hokkaidō Brewery is a 40-minute train ride from Sapporo; take the JR Chitose line towards the airport and get off at JR Sapporo Beer Teien Station. There are a few luggage-sized lockers here if you're coming from/going to the airport.
Note that they are very strict about driving: if you plan on driving, you will not be allowed to have a sample.