Myself I believe that it is the symbolism that Jesus is presenting, so I dont think that it matters if the wine is fermented or not.
If it's the symbolism that matters, then let's look at that symbolism.
Jesus said, "How is it that you fail to perceive that I did not speak about bread? Beware of the leaven of the Pharisees and Sadducees." Matthew 16:11
Then they understood that he did not tell them to beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees. Matthew 16:12
Leaven (yeast) was symbolic of evil --- in this case the evil teaching of the Pharisees.
... you are to deliver this man to Satan for the destruction of the flesh, that his spirit may be saved in the day of the Lord Jesus. Your boasting is not good. Do you not know that a little leaven leavens the whole lump? Cleanse out the old leaven that you may be a new lump, as you really are unleavened. For Christ, our paschal lamb, has been sacrificed. Let us, therefore, celebrate the festival, not with the old leaven, the leaven of malice and evil, but with the unleavened bread of sincerity and truth. (I Corinthians 5:5-8)
Having a man as part of a Christian assembly who is copulating with his step-mother, puts a blemish upon the assembly. It may "leaven the whole lump" ---- make the entire assembly evil.
The feast was to be celebrated with unleavened bread (bread without yeast)
The bread and wine of communion symbolize the body and blood of Christ. Christ was completely without sin throughout his earthly journey. That which symbolizes Him should be completely without leaven (yeast), the symbol of evil. So unleavened bread should be used at communion.
Grape juice contains yeast cells. Wine does not. Although wine is made with a certain type of yeast which ferments grape juice, after the fermentation has been completed, the alchohol in the wine kills the yeast and then the yeast and other impurities sink to the bottom of the container. The pure wine is taken off; it contains no yeast cells. For this reason, fermented wine should be used at communion.