Ruling on drinking date and grape juice before it ferments
Question

Is it permissible for the Muslim to drink date juice or heart of palm juice before it ferments, as it has a high protein content and is free of alcohol, except a very small amount?
Praise be to Allah.The fuqaha’ are agreed that with regard to dry dates, fresh dates and raisins, if each one of these on its own is soaked in water, then it is permissible to drink that water, so long as it will not cause intoxication, and this is what is called nabeedh.
It was narrated that Abu Sa‘eed al-Khudri (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever among you drinks nabeedh, let him drink it made from raisins on their own, or dried dates on their own, or unripe dates on their own.” Narrated by Muslim (1987).
Rather this nabeedh is prohibited if it becomes strong and turns into khamr (wine, intoxicant). But before it becomes strong, drinking it is permissible.
Shaykh Muhammad Saalih al-‘Uthaymeen (may Allah have mercy on him) said: Is grape juice, orange juice and so on haraam or not?
The answer is: It is undoubtedly halaal, unless it has begun to ferment and developed foam on top, in which case it is haraam, or if three days have passed according to the well-known view, even if it has not fermented; it still becomes haraam. They said: That is because after three days, juice usually ferments, and because fermentation may not be apparent, the ruling is based on what usually happens, which is that fermentation occurs after three days.
But the correct view is something other than that. The correct view is that it does not become haraam after three days, especially in cold countries. But if it is in a hot country, then after three days it should be examined, and to be on the safe side it should be avoided and given to animals and the like, because there is the fear that it may have fermented without you realising.
End quote from ash-Sharh al-Mumti‘ ‘ala Zaad al-Mustaqni‘ (14/305, 306).
With regard to small ratios of alcohol, that does not matter, unless it has the effect of making the drink intoxicant. Any drink that causes the drinker to become intoxicated comes under the heading of khamr, which is haraam. Even if intoxication only occurs when a large amount is drunk, consuming it is completely haraam.
For more information, please see the answer to question 146710 .
And Allah knows best.