I spent a week training fasted when on holiday. I trained first thing in the morning.
I was significantly weaker and felt nauseous every session. My workouts were significantly easier yet I found them harder than the much more rigorous workouts that I would usually put myself through.
In theory if I did them for long enough I should notice some form of adaptation to them. If I was forced to train first thing in the morning due to my work schedule then I would do it but I don't believe fasted training offers any advantage in terms of performance.