Various sports media outlets today carried a mildly amusing story about the distress that Toronto Blue Jays pitcher J.A. Happ apparently feels about buying milk in Toronto. As a public service, here is a brief tutorial on the how and why of bagged milk.
In Canada, from Ontario east to the Maritimes, plain milk is commonly sold in, and consumed from, transparent or translucent plastic bags. Consumers can buy a set of three milk bags, totalling 4 litres (slightly more than one US liquid gallon), which come tightly packed into a larger poly bag. In order to use these bags, one must have a matching open-topped plastic milk pitcher. One does not directly use the floppy, flimsy bag. (Mr. Happ apparently missed out on this vital point, somewhat ironically as he is a pitcher.) Most eastern Canadian homes have several—the primary duty pitcher, plus at least one backup that gets used to wash soap from kids' hair, bail water, or to hold miscellaneous small items. Almost any grocery store has these pitchers for sale, although at this point, any nth-gen eastern Canadian probably has a pitcher given by a parent for their first household.
What to Do
Once you get your 4L of milk home, remove and discard the big bag's plastic closer tag, and place one of the 1 1/3L milk bags into your plastic pitcher, and then rap the pitcher smartly on the kitchen counter two or three times to seat it. (Two sharp smacks will do it, but prudence usually dictates a third. One need only experience a full bag departing the pitcher in mid-pour to develop a cautious attitude.) Once the bag is seated, carefully clip off one triangular tip of the bag to form a spout. Clipping the optimal spout is an acquired skill, quickly learned from trial and error. Carefully dispose of the resulting clear plastic nipple, especially if you have babies or pets in the house—choking hazard! You may now carefully pour the milk. A smooth pour is another skill that develops with practice. Store unopened bags and unused milk in the fridge, pitcher and all. When a bag is empty, rinse and recycle where allowed (see below). Put in a new bag, When you put the third bag in the pitcher, add 'buy milk' to your task list. Repeat as needed.
What Not to Do
Do not use the bag without a pitcher. Even with the bag properly seated in a pitcher, do not try to chug milk right from the bag as if it was a carton, unless you are very shapely and mostly naked, and you are about to take a suggestive photo while the milk runs in streams down your chest. Because it's totally going to do that.
Bagged milk was introduced to Canada in 1967 by DuPont, but didn't catch on big until Canada went metric in the mid to late 1970s. Converting to bags was more economical for dairies both from a conversion standpoint and from a total cost-of-materials standpoint. By providing a large amount of milk in one transportable unit, but segregating it into three individual units, a good balance is achieved between convenience (trips to the grocery store) and freshness.
In many regions the outer and inner plastic bags are recyclable (Toronto accepts them in blue bins, for example. Please rinse the inner bags out first!). Other municipalities treat the inner bags as waste. Proponents of plastic jugs cite the jug as superior because it can notionally be reused, however, any returned jugs are shredded because the dairies can't be sure you didn't use the jug for nefarious storage purposes (turpentine, whole blood, gasoline) before returning it. (Note that the fact that your gross roommate likely didn't drink right from the bagged milk pitcher is a big plus of the bag delivery method versus the jug.)
All popular types of plain milk (skim, 1%, 2%, and 'homo milk' (3.25% milk fat, formerly 4%)) are sold in the 4L bag-of-three-bags format. Cream, chocolate milk, soy milk, ostrich milk (j/k), lactose-free milk, and other low volume items are sold only in the wax cartons more familiar to Western Canadians and Americans. Regular milk can also be had this way, and is a more practical size for a single person living on their own. Families, however, almost universally prefer the bags, and bags account for around 75% of all milk sold in Ontario, Canada.
Milk is the only widely consumed liquid commonly sold in bags in Canada. Beer generally comes in bottles or cans, although the Chinese apparently have bagged beer; fruit juice comes in jugs or cartons. (Whole blood is shipped in plastic bags (and in meatbags), but is not generally viewed as a consumer item.)
decoy hunches says: In parts of Africa alcohol is sold in bags as well.
Way too long for BQ'16, I tried, but there's just too much to say.