If work leads to fatigue that prevents the individual from fasting, one should not work temporarily, work at night or find similar ways that one can maintain the ability to fast. A believer is urged to look for such alternative ways. Almighty Allah said: “And whosoever keeps his duty to Allah, Allah will appoint a way out for him, And will provide for him from (a quarter) whence he hath no expectation”. (65:2-3). If one cannot obtain alternative ways, it is better to travel the Sharia-prescribed distance to be regarded as a traveler, so he can break his fast and make it up later when fasting is easier.
If the two cities are both your permanent hometowns, then you should fast in both of them. If your hometown was one of them and your connection to the other city is temporary, for a month or two for instance, then you should fast in your hometown and not fast in the other.