I haven't taken it yet but friends who have said you can't bring ANYTHING with you into the test room..and if you bring an extra piece of clothing you HAVE to wear it..i.e. u can't hang it on the chair - yeah ******ed I know. So it would seem that it would be best to wear something you can zipper for optimal temperature control.
As for eating, I 'm a big fan of powerbars - like eat a piece during breaks to keep the glucose going. I probably won't leave the exam room after every block maybe every 2 blocks) because I hear there can be traffic jams because you have to sign OUT & IN everytime (yeah can they make this any worse?).
Most centers will let you leave for lunch but I did hear of at least once center where you could NOT leave the building (this was in the bay area in cali). PLus u might run of time, so I think it's best to try to bring as much food for yourself as possible...
bonnie