没区别
eat 和have 都可以表示“吃”,但是have意思更加广泛,可以表示“有,从事,允许,喝”等含义.
eat作“吃”解时,一般是指吃固体食物.
We eat rice every day.我们每天吃米饭.
They eat a lot of / often eat potatoes.
She likes eating dumplings.
eat也可用“喝”解,后多接soup（汤）.强调动作,多用于美国英语中.
2.have作“吃”解时,主要用于一日三餐（breakfast,lunch,supper）之前,或与meal连用.
We often have lunch at school.
have用在口语中表示请求或邀请的句子里,也可表示“喝”.
Would you like to have a glass of milk?你想喝杯牛奶吗?
Let’s have a drink of tea.咱们去喝点茶吧.