the doctor tells me (not eat) sweets because I have a toothache.

问题描述:

the doctor tells me (not eat) sweets because I have a toothache.

正确;not to eat
tell sb. (not) to do sth.告诉某人(不)要去做……

固定搭配,tell sb to do sth
tell sb not to do sth
既然提示not,那么就是not to eat.你主要记得上面的两个固定搭配就行了