A flight from Kastrup Copenhagen to Sonderborg, which has 0 stops, is 701﷼ which is the least expensive round-trip domestic flight that Alsie Express offers. For a one-way domestic Alsie Express flight, the cheapest route is Sonderborg to Kastrup Copenhagen (0 stops) for 329﷼.
Alsie Express does not have flights from Doha Hamad Intl at the moment. There are scheduled flights with Alsie Express out of Kastrup Copenhagen though (if you don’t mind flying from this airport). Flying with Norwegian Air International is recommended if you still want to fly from Doha Hamad Intl.