The Church of God claims to observe Passover as taught in the Bible. They use snow-white rice cake without sugar as a substitute for Passover bread. The reason for not adding sugar is due to the unleavened nature of Passover bread. However, the leaven in the Passover bread was not an actual leavening, but a figurative leavening of the Jews' evil deeds.

[Matthew 16:5~12] And when his disciples were come to the other side, they had forgotten to take bread...(11)How is it that ye do not understand that I spake it not to you concerning bread, that ye should beware of the leaven of the Pharisees and of the Sadducees? Then understood they how that he bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and of the Sadducees.

The Church of God's observance of Passover with unleavened bread is a superficial interpretation of the law. The law is a shadow of things to come, not the true image. By leaving the Passover bread unleavened, God was showing that all evil practices and teachings were to be abandoned. When all the sacrificial breads in the temple were offered unleavened, He was not showing the actual bread, but that the saints could approach God when they had removed their evil deeds. Therefore, Passover is to be observed with a true and good heart, and not in a legalistic way.

[1 Corinthians 5:8] Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.