There are other words used ... For example ... Acts 2:13 uses γλευκους for "new wine" or "sweet wine" ... and 2:15 makes it clear it was not grape juice.
Jesus also used the phrase "fruit/produce of the vine" ... γεννηματος της αμπελου.
I suppose one could argue that there is nothing in the text of Jesus' statement in Matt 26 that demands fermentation; but Acts 2 seems clear.
Also, I recall notes from a lecture that mentioned the Jews DID have ways to prevent fermentation of grape juice.
You bet. They drank it immediately. Grape juice in a warm environment will start fermenting within a couple of days. Native yeasts cover the grapes as they are growing, and they stay during pressing. Even more are present in the air on the wind. No getting rid of them.
Same thing with cheese. Milk spoils. Cheese keeps for much longer.
That's irrelevant to our discussion. The fact is that they drank alcoholic beverages. What they could or couldn't do is immaterial. They even occasionally got intoxicated. Remember Noah? How about Lot?
God endorsed consumption of alcoholic beverages. (Deut 14:26; Prov. 31)
The whole point of the discussion is that righteous men drank alcoholic beverages, righteously.
The bible uses “neos oinos” for “new wine,” by which was plainly meant grape juice which had not fermented. The Greek word in 2:13 is “gleukos,” which meant sweetness, or sweet wine, which, as you note, was certainly alcoholic.
John 2 depicts Jesus making alcoholic wine; it was noted that it was good stuff, causing the waiters to wonder why it was saved to the end, since people usually save the cheap stuff towards the end. The plain reason for this is that once people have been getting a little drunk, you can pass off lower quality wines... which in those days meant lower-alcohol wines caused by less sweet grapes.