How to call custom fields in Google Maps bubbles?

We are using Google Maps on our site and need to be able to customize the data that comes in on the bubbles when you click a pin. I’m not sure how to call those custom fields, the only thing I’ve got so far is the link and the post title.

The code below is in the functions.php file and has dummy data in place of where we need the custom fields to go, I just don’t know what to put there:

if($node == "events")
                        {
                        $html = "<a href='".$post->post_name."'>".$post->post_title."</a>";
                        $html .= "custom-field <br/> <br/>";
                        $html .= "<a href='custom-field' target='_blank'>"."<h1 style='font-weight: bolder; font-size: 14px;'>Get Directions</h1>"."</a>";
                        }

Any idea? Thanks!