Falls somewhere between medium/small/smaller sized city. Might have felt different about it if during visit had different mental state, or visited on different month, or was younger/student/alcoholic. You can have a lot of ifs, but in the end I can't find a good reason why I would want to return to this city.
The currency is Romanian Lei (RON). The rate is about 4.6 RON for 1 EUR, 46 RON for 10 €, 100 RON for 22 €.
You can get a local SIM card from Orange for around 5 € with 14 GB data and calls/SMS.
Another alternative would be to get a card from Vodafone.
Could not find good places to eat (you get food which you move with fork for couple minutes thinking if you should eat). Find it much easier to buy some ground beef and vegetables to make some meatballs at home while listening to some podcast.
There is a steam punk cafe which you might want to visit because it has cool looking interior.
Central Park Cluj good park to walk around if the weather is nice. Looks cool at night.
Oncos Tonus Gym a crowded gym were some of equipment is broken and the rest is strange functioning. Good to get a basic exercise for 10 RON (~2.17 €).
Bamboo Fitness and Spa a fancy looking gym which breakes that image when you notice black spider webs from vents or live electric wires sticking from walls. Spacious gym with lots of equipment. Single use is 20 RON (~4.35 €). Does not allow to exercise with barefoot shoes, so fuck them.
Traffic / Walking
You can get an Uber from airport using free wifi.
Walkability of the city is bad, a lot of streets are wide enough only for a single person and they are often blocked by a random trash can or street light. Lots of people smoke so often you end up having to smell it. Cars stop at the last moment, crossing streets does not feel safe unless it's controlled with light but in that case you end up waiting a long time for green light.
A lot of places close during the weekend, plan accordingly.
Iulius Mall is good for buying some basic stuff you throw away to travel light (sweatpants, slippers, scissors, etc.). Also has electronics shop.
I visited during November. The weather most of the time was bad (cold). There was some really bad days where it was raining or the wind was so strong that it was throwing small rocks into your face.
For other locations in the world see intro article.