If someone has a sweet tooth, he or she likes eating many sweet foods like candy and cheese cake. have a sweet tooth，千万别理解为“我有颗甜甜的牙”或是“有颗一吃甜食就会痛的牙”，它的真正含义是“某人爱吃甜食”。推而广之，也可以说have a spicy tooth(爱吃辣的东西)；have a salty tooth(爱吃咸的)等。

Examples:

Fruit is a good substitute for candy if you have a sweet tooth that just has to be satisfied. 水果是糖果的绝佳替代品，如果你喜好甜食，也能够满足你。

John can’t resist chocolate and cake all the time. He must have a sweet tooth. John总不能抗拒巧克力和蛋糕。他一定是个甜食爱好者。