At this stage MYOB Essentials doesn't have any sample data available through the API. However it's a simple online tool and really quick to create content for.
Development for Essentials works off the Trial account setup within Essentials. To get up and running quickly sign up for a 30 day free trial here.
I am a paid developer and want a full Essentials Account
Easy, drop us a note through the Submit a Ticket button (top right of this page) and tell us the ID for the Essentials file. The quickest way to get this is to login into Essentials and take the ID from the URL.
Our team will sort you out quickly and easily.