是They think don`t eat breakfast还是They think not to eat break

都不对,纯正英文不这么说.
可以说:
They don't intend to have breakfast.
They don't intend to have breakfast as they want to have more sleep..
They don't want to have breakfast.
They don't want to have breakfast so they can get more sleep.
一定要用think的话,应该为:
They don't think they need breakfast.
They don't think they need breakfast as they want to have more sleep..

they don't think 才是正确的表达方式。

they think not to eat....或者they don't think to eat...