I need help finding a book, my memory is very garbled so I apologise in advance.
I remember reading in the distant past, a book beginning with the word E, not too sure if the word was equinox. But the book is about a bunch of kids taking part in a test to participate in a game produced by someone.
The main character when asked what he would choose to bring along with him, chose a vial filled with water. Those chosen later go on and enter the game, only to find out the game could have impact on reality, ie. manifesting objects obtained in the game in reality and that the creator created the game for the sole purpose of bringing out a vial so as to cure his daughter of her illness. They bring out several vials with a few cracking and I think there were 3 they brought out in the end.