Sofia is a city with long history. You may need at least 3 nights to enjoy it and its nearby spots. There are many events you can do, a city walk tour (this one is always my favorite, because you are shown around the city by a local person), a day-trip outside Sofia (there are many choices, depends on what you like), or just wondering around the city by yourself and discover interesting things or just taking photos.
Rooftop bar in 4star Sense hotel was great - sometimes Sense hotel is almost as cheap to stay in as some 3stars!
Do the Free Sofia tour. Definetely a highlight and the tourguides are very professional. It is free but do tip the guide! There are some interesting restaurants in Sofia and worth a visit.
Cactus, Hadjidrasanovite are a couple of good places but I am sure you will some more if you explore.
There are a few sightseeing spots in the city, but Rila Monastery (outside Sofia) is the must-see. In general, we found the food good and nightlife quite vibrant.
Just ignore the miserable locals. Enjoy the cheap prices. Bulgarians do little to be happy a bunch of depressives.
My God i loved this country i loved Bulgarian people ..It was my first trip to Bulgaria and i was not sure if im going to enjoy it but after i left i wished to return back i loved the nice hospitality and lovely people , nice weather , very tasty food , quite and lovely city i can write a book about this beautiful city and lovely country , i shall plan my holidays to visit every year .
Thank you BULGARIA