Only neanderthals take their juice bottle out of the fridge, pour a glass and place it back in the fridge. The evolved life hacker attaches a tap to a container that fits perfectly in the fridge to conveniently pour any drink.
Sure, you can buy something that serves this purpose, but everyone's fridge space requirements are different. Redditor macgyveredd's hack lets you choose the best container for your needs, and then it's a simple matter of attaching a tap where it is most convenient. It's just a basic food-safe plastic container with a push-type tap. But, as macgyveredd points out, the other benefit of this is cleaning:
Also much easier to clean inside (take off the lid and put it in the dishwasher). If you put milk or juice or alcohol in those other containers, it will be hard to clean the inside later.
If the store-bought solution works for you, it's a good way to make your fridge more convenient. If your space requirements are a little different, just make it yourself. It shouldn't take you much time.