A. From grapes and olives:
Forbidden to be drunk on Shabbos: Liquids which flowed out on Shabbos on their own from olives and grapes are forbidden [to be eaten] until evening [i.e. after Shabbos] due to a decree that one may come to squeeze them with his hands in order to drink them today [on Shabbos] if [these liquids] were to be permitted.
[Furthermore] even if the olives and grapes [from which the juice flowed from] are designated to be eaten [and not squeezed] [nevertheless] we suspect that one may change his mind to squeeze it for its juices just like is common for majority of olives and grapes.
If the grapes and olives were crushed from before Shabbos: Olives and grapes which were crushed from before Shabbos, the juice which comes out from them on Shabbos is allowed [to be drunk] for the reasons explained in chapter 252 [Halacha 14]. [However this only applies if one began crushing the grapes and olives a while before the commencing of Shabbos, to the point that by the time Shabbos began the grapes and olives were already crushed. If however one began crushing the grapes and olives right before Shabbos began, such as he placed a heavy board on top of them right before Shabbos, then their liquids remain forbidden to be eaten on Shabbos.]
If the grapes were in a vat of wine: [Furthermore] even if they had not been crushed from before Shabbos, if there is wine in the vats that the grapes are inside of, then even though the grapes break open on Shabbos inside the vat and more wine comes out [from them into the vat], [nevertheless] one is allowed to drink from this vat on Shabbos, because every little bit of wine which comes out of the grapes on Shabbos becomes nullified against 60 times the wine that was already in the vat [from before Shabbos].
The reason that the wine is not considered a Davar Sheyeish Lo Matirin: Now, although this wine [which flowed on Shabbos] is considered an item which will eventually become permitted [ in which case it should never be nullified until then] being that after Shabbos it will be permitted without any nullification [needed], nevertheless since this wine that came out on Shabbos was never recognizable prior to it being mixed [into the vat] and it [thus] never had the status of wine on it (look in Yorah Deah chapter 123 regarding when juice from a grape receives a status of wine) [therefore] it does not receive the status of an item which will eventually become permitted [without needing nullification] until after it already became nullified [within the wine that it seeped into], and [the Sages] only said that something which will eventually become permitted is not nullified in a case that the prohibition was initially visible and it already then received a status of something which will eventually become permitted and then afterwards got mixed [into another food].
If one placed the grapes into the vat on Shabbos: [Furthermore] even if one placed whole grapes into the vat on Shabbos and they then broke open [and seeped wine] on that day into the wine [that was already in the vat], it is permitted to drink wine from the vat for the above mentioned reason.
However it is initially forbidden to place whole grapes into wine on Shabbos in order so they split open and ooze their wine [into the vat] due to the prohibition of squeezing, as although he is not squeezing it actually with his hands nevertheless it is Rabbinically prohibited [to cause it to be squeezed].
Grape seeds and skins: Grape seeds and skin which had water placed on them in order to make grape-skin, wine it is permitted to draw [wine] out from these [seeds and skins, into the water] and then drink it.
Furthermore even if one had not placed water [onto them] and the wine squeezes and flows out on its own, it is permitted to drink it being that it already was broken up before Shabbos.
B. From other fruits:
Juice which has flowed from strawberries and pomegranates and the like then if they are designated to be eaten then the liquid is permitted, as we do not suspect that one may change his mind to [use them] for juice. However if they are designated for their juice then the juice is forbidden.
Summary-Juice which flowed on their own from fruits on Shabbos
- From grapes and olives:
Are forbidden [to be eaten] until after Shabbos, unless:
- The grapes/olives were crushed from before Shabbos
- They are in a vat of wine or oil
The juices of grape seeds and skins that have flowed on their own are allowed.
- The grapes/olives were crushed from before Shabbos
- From other fruits:
If the fruits are designated to be eaten then the liquid is permitted.
If they are designated for their juice then it has the same law as grapes and olives.
 The reason for the allowance in such a case is because even if one were to come to squeeze these olives and grapes on Shabbos, which is the suspicion behind the prohibition, he would not transgress a Biblical decree being that the fruits are already crushed and their liquids would flow regardless. Thus by squeezing them one is merely hastening the process, of which doing so is only a Rabbinical prohibition. [252/14]
 As we suspect one may come to squeeze them on Shabbos, in which case doing so involves a Biblical prohibition being that they had not at all been crushed from before Shabbos.[ibid]
 So rules the Taz. However the Magen Avraham and Chayeh Adam and Mishneh Berurah  rule that it is allowed to be done even initially.
 What does this mean? May one squeeze them? In next Halacha it is explained that it is forbidden to squeeze absorbed liquids.