两句都是正确的
I ate the apple that you gave me.
that you gave me是修饰apple 的
把从句改成陈述句语序就是
you gave me the apple
而第二句则是you gave the apple to me
give 可以接双宾语,即give sb sth,可以把sth提前,用that+sb do sth来修饰
一般用第一句的形式,但是在语法上两句句子都正确
而第一句比较普遍,符合大多数不能接双宾语动词改定语从句的形式
举个例子：
I read the book you lent me.
而不能写成 I read the book you lent to me.
这两种形式都在这句句子里都可以用.