I'd say vodka and snaps, as far as tradition goes and in terms of what Sweden has produced historically. But when I visited, it seemed like beer (especially the big Swedish and Danish brands) and wine were definitely the most popular. One must buy any bottled beverage over 3.5% ABV at the government-run Systembolaget stores, but it's a pretty good monopoly in the sense that there's a very wide selection and a usually very attentive staff, and word is they'll special order almost anything if they don't have it in stock. Also, craft beer seemed to be really catching on, so, at least from my experience, the Swedes are very open to beer from all over the world. I was super-happy finding good Michigan beer in Sweden!