Why did Jesus the Son of God choose wheat bread and grape wine for the Eucharist? The reasons are numerous.
1. As foods preferred by the wealthy, there would always be wheat bread and grape wine available, throughout the future of the world, even during the most difficult Last Days when Christianity would be outlawed.
2. Wheat and grapes can be grown in rural areas, if Christians have fled during persecution. They can be grown in almost any region of the world. They can be harvested by hand.
3. Symbolically, wheat turns into bread just as the natural human person turns into a Christian, who lives by supernatural grace. Then the grapes turn into wine as a similar symbolism. One simple natural thing turns into another better thing.
4. Wheat and wine work well as symbols of body and blood. The symbolic separation of bread and wine indicates the shedding of blood in the sacrifice of Christ.
5. Wheat is taken from an essential food for much of humanity; whereas wine is taken from a non-essential food expressing a joyous occasion, such as a wedding. So we have the symbol of daily necessity, daily bread, and then the symbol of a great celebration, on a momentous occasion.
6. These are two of the oldest foods in humanity, and also foods that will continue until the Return of Christ. So they symbolize Adam and Eve as well as the Return of Christ for the future Resurrection.
7. These foods keep well, without refrigeration, and they are healthy foods.
I’m sure there are other reasons, known to other human persons but not to me, and further reasons known only to the all-knowing unfathomable wisdom of God.