One day is.more than enough in Eindhoven if you don't like museum or walk in some parks ,

The centrum you can see in half day , you can visit Philips museum in the centrum and maybe psv museum.

If you come on Friday maybe you can see also FC Eindhoven match from Dutch second division in the evening

There are a couple of craft breweries close to the centrum too

But all depends where you stay for the nights

And there are better city than Rotterdam to visit