Jon: As a reward for staying on your diet, I'm going to allow you to have some sugar with your coffee today.
Jon: Let me rephrase that.
reward n. 奖励
stay on 保持,持续做某事
He resigned as chairman, but stayed on as an instructor.
他辞去了主席的职位，但仍然做导师。
allow sb to do 允许某人做某事
My boss doesn't allow me to use the telephone.
老板不许我使用电话.
rephrase vt. 重新措辞, 改述
Let me rephrase the question.
让我重述下问题。
【参考译文】
乔恩: 作为你坚持节食的奖励，今天我允许你喝咖啡时加些糖。
乔恩: 我得重述下所说过的话。