You will be given time to go to your tent (if you bring one) or to climb in your bivi to sleep.
Brine either an air mattress or a sleeping pad youll be more comfortable then in your car.
Bring food (mre's are good for the most part ask the dealer what ones are good. I like chicken fajitas beens n winers and beef stew. Avoid the egg ones lol)
Also bring some real food (steak or chicken and bacon n eggs) for the night befor the game and the morning after (bring extra bacon for yer teammates they will love you)
Extra pants socks boots undies and t shirts incase you get wet
Edit read this too http://www.airsoftcanada.com/showthread.php?t=152415