Thank you for your question.
Here is the list: fruits, vegetables, yogurts, juices and plenty of water.
Raw vegetables, if you are used to that.
You can accept those from anyone at any time and those items will be beneficial for your health. If you could use the kitchen of the hostel, then you can prepare your own meals in your own pots. I have done that while living in a hostel in India for about a month.