pick up rent a car from germany, go to hungary, change the car, go to Bulgaria.

I know there are rental car companys which let you go to Bulgaria in hungaria. Im not shure but maybe sixt is one them.

For company drivers is it also possible to get special permission for german rental cars to go to bulgaria. I know for sure that if Siemens ask to send a driver to bulgaria with sixt car, he will go!

cheers