You can bring a book bag, but they'll probably make you put it in the front of the room before the test starts, so you may not want to even bother bringing one. They let us keep a bottle of water under our seats, but we couldn't touch it until the break. What I did was wear cargo pants, that way I could keep a snack handy for the breaks. You can put whatever you want in your pants, it's not as though they pat you down or anything. (Hmm....that didn't sound quite right). Anyway...good luck tomorrow!!