@f0zzyNUE I just bought a ticket for direct turnaround: BUD-IST-JFK-IST-BUD... Already ticketed.
@Asienlee If TK will sell you the ticket then they should give you a BP. @ KWI there is a transit desk where the airport staff is printing the boarding passes.
It worked for me When I was connecting there and needed a Pegasus BP. Remember that you can't have any checked-in luggage.