Sonderborg is just a small provincial airport. It's not very busy, though there are scheduled ATR flights to Copenhagen (Cimber Air has it's HQ there). There is also a corporate jet charter outfit and a single flying school.
The food at the restaurant is OK.
The Danish ATC are well spoken and helpful.
But why Sonderborg?
You could go a little further up to Billund, Legoland is walking distance from the airport or to Stauning where there is a nice museum on site.
Have a nice flight.