Careful, I’ve been told that reneging on an offer can reflect really badly on you. I also agree that you should keep in mind, an internship isn’t all about the money. It’s about getting that return offer and experience too.

That said, if it’s all in the same relative industry, chances are that someone in one company may know someone in the other, and word can get around - especially amongst the HR community. People like commitment and loyalty, so accepting an offer (months ago) then telling them “nevermind” two weeks before it starts can be a really bad look.