Serve another(standalone) page or static file in website built with react

This should work:

const reload = () => window.location.reload();

<Router>
  // all your routes..
  ...

  // Your special routes..
  <Route path="/sitemap.xml" onEnter={reload} />
  <Route path="/something.html" onEnter={reload} />
</Router>

So, I think this should be pretty clear what it does ;)

Update:

if this is an option you can simply put target="_blank" attribute in your <Link>

IMHO this is from the UX perspective even better, because if these routes are not part of your main application, the user can just switch the Tab after visiting that special pages.

It's an unwanted behaviour of ServiceWorker.js use the comment below and change it in index.js of your React proyect and it should work

import { unregister } from './registerServiceWorker';
unregister();

https://github.com/facebookincubator/create-react-app/issues/2715