Sahih al-Bukhari Book 74, Hadith 27
The Prophet (ﷺ) forbade the drinking of alcoholic drinks prepared from raisins, dates, unripe dates and
fresh ripe dates.
While I was serving Abu Talha. Abu Dujana and Abu Suhail bin Al-Baida' with a drink made from a mixture of unripe and ripe dates, alcoholic drinks, were made unlawful, whereupon I threw it away, and I was their butler and the youngest of them, and we used to consider that drink as an alcoholic drink in those days.
The Prophet (ﷺ) forbade the mixing of ripe and unripe dates and also the mixing of dates and raisins (for preparing a syrup) but the syrup of each kind of fruit should be prepared separately. ( One may have such drinks as long as it is fresh )