May one open a juice box container on Shabbat where to open it one has to turn the cap and thereby puncture a whole in the container?
Turning the cap punctures the container making a proper size hole making the container into a useful utensil which is forbidden on Shabbat. (See Shabbat 146a, Shulchan Aruch Hlchot Shabbat 314:a). The Shmirat Shabbat K'hilchata chapter 9,suggests that if one forgot to open the container before Shabbat one can make a hole on the bottom of the container or in its side and transfer the contents elsewhere. Similarly, in the case of this particular container I have heard some poskim, suggest, that rather than turn the plastic which makes a precise hole which is forbidden on Shabbat, tear the spout from the side which shows that the intention is to no longer use the container.