How to get and serve HTML fragments?

I was wondering how can I render an HTML fragment which is not a component...

For example:
Let's say that `example.com/esi-fragment` is serving

```

So, as per ESI i can do something like this in an example.com page

```

```

And I should see the div rendered in my page.

In all the examples I see online I only can see react components rendered... Which is working, but not really what I want to do.... Is there something I'm getting wrong?

Thanks!