1) Go to a gym open long hours convenient to your train, home or work.
2) Eat on the train.
I had crazy hours and a 3 hour daily commute but I easily made it work given relatively convenient gym locations. (It helped having a desk job with minimal travel.)
For several months my initial round of working out I used to go to a Golds right next to my train station, which made it easy to park in the gym lot for the day, lift before work and, on the hour ride into Manhattan, drink my protein shake and eat my hardboiled egg whites, which as you can imagine made me real popular amongst my fellow passengers. The, after eating a salmon wrap dinner on the train ride back (again, call me Mister Popular but this was the pre-texting cell phone era where everybody was rude) and being forced to be right back on the gym premises in their lot to pick up my car, I'd then train in the evening (yoga, swimming or abs) no matter how late it was.
Then I figured out that if I went to the Crunch, which I passed between Penn Station and my office in Times Square, I'd get platform level covered parking right at my more local train station closer to the city. That killed the nighttime workouts except for swimming two nights a week at my suburban Y.
The big culture shock was that when I went to Crunch the hot members looked a little "off" - their bodies were more refined but their faces looked a bit haggard. Then I realized that in the suburbs the members were in their teens-20s and in the city, 30s-40s.