I think saying, "You can drink directly from the bottle" is appropriate enough. As for "hole," I would say that's not quite accurate. You see, "hole" is for something small. A bottle's opening, however, is not small enough (in respect to the whole bottle) to be called a hole. You could say the opening of the bottle. Another way would be "mouth" of the bottle, as in, "You can drink directly from the mouth of the bottle." There probably are other ways of saying that, too.