There is absolutely no food available once the train leaves Mumbai.. not even water bottles. It's highly recommended that you take your food and water before boarding the train.
For the second day lunch also, orders are taken and lunch is served at Jetalasar. Price Rs. 70 (Quality is questionable though)
To avoid this, lunch can be bought at Rajkot.. lot of options are available at PF#1. Thali is available for Rs. 90 which is far better than what is served at Jetalsar.