if you travel for short period i.e. for one day then you can carry food with yoy, if the journey is too long like Jammu Tawi to Kanyakumari which takes more than 3 nights then the food from railways or vendors can be taken. Please take food from station vendors that food may be better than train pentry food as they always use quality of water = toilet water as the tanks are same. rest Rajdhani / Shatabadi food are better than pantry car food.