Why can’t one open bottles on Shabbat?
The reason for not opening bottles on Shabbat is that when one opens the bottle one makes a Kli. The cap of the bottle was never a cap as it was a piece of metal that was melted onto the bottle; it becomes a cap when one opens the bottle. Making a cap is forming a new Kli which is forbidden on Shabbat. The solution to this is to make a hole in the cap before opening the bottle thus, not making a Kli that can be used. Bebirkat Hatorah, Rabbi Ya'akov Ariel