2000 years ago there was no way to preserve grape juice as Welch's does, so there was not way in the world that the fruit of the vine Jesus served in the cup at Passover was unfermented. The harvest is in the fall, and passover is in the spring.
Jesus Himself referred to His own consumption of fermented wine.
Matthew 11:18-19:
18 For John came neither eating nor drinking, and they say, He hath a devil.
19 The Son of man came eating and drinking, and they say, Behold a man gluttonous, and a winebibber, a friend of publicans and sinners. But wisdom is justified of her children.
A winebibber was a drunkard. So Jesus said that they accused John because he didn't eat meat or drink alcohol (presumably because he was a Nazarite) while they accused Him of gluttony and drunkardness because He did eat meat and drink alcohol-containing wine. He was pointing out their hypocricy, trying to have it both ways, but the passage makes no sense if they hadn't seen Jesus drinking wine.
Again, there was no way of keeping grape juice from fermenting. There was a whole culture around vineyards and wine in that day, as there has always been in countries around the Mediteranean. Jesus lived in that culture. And the comments at the marriage at Cana make no sense unless the wine contained alcohol. People don't compare and comment on the quality of sweet juice.
Those who insist that something is a sin where there is no scripture calling it sin are adding something that isn't there. Being a drunkard is condemned. Just as being a glutton is sinful, but eating is not.
If you wish to, you could insist that somehow Jesus miraculously preserved grape juice until the spring to use at the last supper, but such a miracle would have been noted in scripture I think. Without a miracle, how would the juice have been preserved for at least 5 months without fermenting? No refrigeration, no chemical preservatives, no canning process. How could it have been done?
My .02 cents from a Biblical perspective.
