darchei noam- first, there is a material difference between shabbos and yom tov. I suppose that on yom tov it is muttor accordign to all poskim-as it is clealry oichel nefesh.
as far as shabbos- this a part of a larger quuestion of opening cans on shabbos. I remember that years ago, the Tselemer rov zz’l (big possek in Williasmburg after the war)allowed to open cans (sardines, beans, etc)as long as you threw away the can and never used it. Additionally, if it was a small can (such as tuna or sardines)then it weould never become a kli anyway, so there was an additional reason for the hetter.Some poskim had problems with large cans as they could be used afterwards (for storage,even cooking) and advised to make a small hole in the UNDERSIDE of the can before opening it up and in this way, there was no possibiliy of making a kli.
I don’t understand the reasoning of those poskim who say that, because you drink from the can, it is considered a kli. if this is the reasoning, then any can or container is a kli even BEFORE you open it up.Anyway- i welcome any views on this.