Actually, in Yugoslavia there was some confusion about what's yogurt and what's sour milk. What passed under that name in the east was called the other name in the west and vice versa. So we'd usually buy the wrong kind on vacation, at least once every year.
The culture is somewhat different, and so is the recipe. For serbian yogurt it takes the starter culture, the milk needs to be thinned, somewhat salted and the result is there in about 12 hours - the liquid yogurt. Similar to turkish one, except that's saltier and thinner.
So Yugoslav (well, east of Croatia at least) yogurt is a beverage. IOW, drink it. Shake it first, it may have separated the more liquid parts on top. Shake first, then open it. Everyone will know a couple of stories about people who didn't quite follow this last bit of instruction, and did them in wrong order.
There are as many recipes on how to open a yogurt as some people have about making tea or coffee. Some tear off the lid, some tear a hole sized half teaspoon. Some use their keys and drill two holes on opposing ends - one to suck yogurt through, the other to let the air in. This recipe is the mustache & beard savior. I invented that trick for myself, but I guess it's been invented many times.
One can't possibly imagine any business functioning without proper flow of jogurt, burek and coffee.
Update 2014: the size of the standard plastic cup is now, in purely orwellian manner, increased from 200 ml to 180 ml for the practically same price. I don't buy those much, I take long swigs from a liter or 1,5l bottle.
Update 2018: now there's a bakers' yogurt (just like there's a hunters' bread - I asked Gavra "when do hunters bake bread?" and he said "never"), which is allegedly better suited to have with bakery products, it being 0,25l. Yeah, right, and 0,2 was exactly that size for about forty years, and now you discovered it's wrong, eh?