Many dairy products are sold in plastic containers. One may peel the cover of such a plastic container. Similarly, packages of wafers and chocolate bars may be opened. Since the wrapper is meant to be disposable, it is secondary to the food inside it, just as an orange peel is secondary to the orange and may be removed in order to eat the orange.
One may make a hole in the top of a bag of milk or juice in order to pour out the liquid, open the top of a bag of sugar that is glued shut, and rip open bags of candies or other foods.
Similarly, we find that the Sages permitted cutting open ĥotalot (palm leaves used to protect unripe dates) on Shabbat. They permitted this because these leaves lacked importance, as they were considered entirely secondary to the dates inside them, similar to an orange peel. (Shabbat 146a; Kol Bo; SA 314:8).
Some are stringent and do not open bags or packages if the food will remain inside for a while, as is the case with a bag of sugar. They maintain that one who makes a neat opening is not ruining the bag, but rather is creating a receptacle (Ĥazon Ish 51:10). According to this approach, the only way to open such bags is to tear them apart entirely and transfer their contents to a different container.
In practice the halakha follows the lenient position, because these bags have no importance and are thrown out after the food they contain is finished. Therefore, one may open them in whatever way enables easy removal of their contents, and he may use them until the food inside is used up.
It should also be mentioned that when opening these bags, one should try not to tear any letters. However, if necessary, one may open the bag even if it is clear that doing so will tear letters (as explained below, 18:3).
Similarly, one may open packages that contain items that are necessary for Shabbat, such as tissues and diapers. It is proper to open them more messily than one would during the week. Those who follow the stringent opinion would need to destroy the packaging so that it can no longer hold its original contents. The halakha is in accordance with those who are lenient.
. The dispensation to tear ĥotalot (Shabbat 146a) is not limited, so even if the opening allows the dates to be removed easily, there is no prohibition. Even in the case of a mustekei barrel (Shabbat 146a; Beitza 33b), one may make an opening through which the contents can be removed over the course of a few days, on condition that there is no possibility that it is a neat opening, which would allow the barrel to be used repeatedly. Therefore, the mishna in Shabbat allows making an opening in the top of a barrel even if it is made to pour out wine. Only if the hole is made in the side of the barrel, where it is clear that the opening is meant to be used multiple times, is it forbidden (Shabbat 146a). Indeed, this is the ruling of SA 314:6. The reasoning behind all these permissive rulings is that since we are dealing with packaging that is meant to be used only once, the container is secondary to the food within it. Thus, it is comparable to the peel of a fruit, which may be cut up and removed with no limitations. Even when the package is large and it will take days to finish up what is inside, as is the case with a milk carton or a bag of sugar, there is no prohibition, as the Sages permitted opening a wine barrel or ĥotalot even though they were not immediately emptied out. (This is also implied in m. Kelim 16:5, according to the explanation of Rash.) It is only if a neat hole is made in the package, in order to allow multiple uses after the current contents of the package are finished, that there is a prohibition. In contrast, when dealing with containers of milk, packages of sugar, and the like, it would never dawn on anyone to reuse them, so there is no issue of Boneh or Kore’a when opening them. Those who are stringent maintain that the dispensation to make an opening is limited to something that is not part of the packaging itself but only adheres to it, like the lid of a barrel; but if one makes a neat opening in the package itself to pour the milk or measure out the sugar, it is like making a receptacle. However, the prohibition is only rabbinic, since the opening only serves for the contents’ removal, not their reinsertion (Ĥazon Ish 51:10; see Orĥot Shabbat 12:6). They are also concerned about Kore’a when opening a bag of sugar, since many maintain that tearing is prohibited if it serves a constructive purpose. However, we have already seen that the law pertaining to a package of food is the same as that of ĥotalot, where the prohibition of Kore’a is completely irrelevant. Some of the lenient opinions concede that ideally one should comply with the stringent position and open packages before Shabbat. If it is necessary to open a bag of milk on Shabbat, le-khatĥila it is better to make a smaller opening than one normally would during the week or to tear the plastic with one’s teeth, so that it is clear that one does not mean to make a neat opening. This way, even some of the stringent opinions would concede that it is permissible.
. The law of opening packages of clothing and the like is the same as that of packages of food (R. Shlomo Zalman Auerbach, Shulĥan Shlomo 314:7:6). Just as one may use packages of food until their contents have been finished, so too when opening packages of tissues or diapers he may use the packages until their contents have been finished. Those who are stringent require destroying the packaging entirely (Minĥat Ish 17:22; Orĥot Shabbat 12:23). According to Yalkut Yosef 314 n. 22, one should not rip the wrapping paper off a book or picture, because those who are lenient only permit tearing a package when the item is needed for Shabbat, and that is not the case here. It would seem in practice that one may do so if there is a need. However, MB 340:41 and BHL s.v. “ha-niyar” prohibit opening a letter even if there is a great need. On the other hand, Maharil, MA 519:4, and Taz ad loc. 5 permit it. Since the prohibition is rabbinic and there is a need, one may be lenient.