Traveling towards Hyderabad, you get good food at Gulbarga station (steaming hot idlis) and also at Wadi. Don't bother buying from the hawkers who board before that. They usually serve cold or stale food.
While traveling from Hyderabad to Bombay, the train caterers usually serve hot pav-bhaji. They start with the AC compartments first then reach the 3-tier sleeper coaches.