Drink Jesus' blood. The devout Jews who listened to Jesus were repulsed by these words. Blood is sacred to the Jews. Blood carries life. If a person gets a wound and the blood flows out of them their life flows away as well.
Blood stands for life.
And life belongs to God. Therefore, blood belongs to God who gave it. A good Jew would not eat any meat unless it has been completely drained of blood. There were rules against it in Genesis 9 and Deuteronomy 15. That isn't kosher.