Whenever you want to pour milk, juice or whatever else is in Tetra Pak, do you miss something? By contrast, this simple trick helps.
Actually, we have already filed our bib long ago and now quite well out, as it is, with the right table manners. Small misadventures such as spilling food, really only happen to us quite, very rarely - except for this one thing that is guaranteed to ALWAYS go wrong:
When pouring from a rectangular Tetra Pak with plastic closure (for example, milk, or juice from the bag), usually something wrong, because the bag when opened practically 'exploded'. When pouring milk pushes into the opening and closes it temporarily. This creates a vacuum that sucks air into the Tetra Pak and displaces milk from the pack. The result: the milk splashes.
On the other hand, a very simple trick helps: Simply pierce a small hole in the opposite corner of the closure. So the pressure on the opening is different and there is nothing wrong with it.