Catering is non-existent except at NDLS where couple of private contractors sell meals few minutes prior to scheduled departure (1945 hrs). There will be no other food/water/tea/coffee till Dhanbad in the morning so be prepared accordingly. I preferred to have a heavy early dinner and board. Simple breakfast provided by travelling hawkers is available at Dhanbad and Asansol but better to carry some biscuits / juice and eat properly on arrival at Howrah (1230).
In general, if you have had dinner and unless you have a small child, the lack of catering is not a major hassle at all.