Based on the preposition that you start and finish your Bulgarian itinerary from the capital Sofia and want to see the maximum possible in five days, the proposed rout might look like this:
1-st day : Sofia – Rila Monastery – Plovdiv (about 320 km.)
2-nd day: Plovdiv – Burgas – Sozopol (about 300 km.)
3-d day: Sozopol – Nesebar- Varna- Balchik (about 200 km.)
4-th day: Varna- Shumen – Veliki Preslav – Ruse- Veliko Tarnovo (about 250 km.)
5-th day: Veliko Tarnovo – Trjavna- Shipka- Kalofer – Karlovo – Sofia (about 230 km.)