改为否定句是I don't have any grapes。这句话是实义动词拥有的意思，改为否定句要借助助动词do，就是由i have转变成i do not have，而some一般多用于肯定句中，改为否定句时要变为any。some和any都表达“一些”的意思。

例句：

I have some snacks。我有一些零食。

I don't have any snacks。我没有一些零食。

I have some old clothes I don't wear。我有一些不穿的旧衣服。

I don't have any old clothes I don't wear。我没有一些不穿的旧衣服。

Jerry has some apples and oranges。杰瑞有一些苹果和橙子。

Jerry doesn't have any apples and oranges。杰瑞没有一些苹果和橙子。