Here's a tip.
Check the rules to be sure, as they may have changed from last year, but on my experience....you CAN bring in a camelbak. It MUST be empty. You CAN bring in bottled water. They MUST be sealed.
Last year I grabbed two of the tall skinny "Smart Water" bottles (seen below with Jennifer) and packed them into the pouch with the bladder in my camelbak, they were a perfect fit. When I got there I showed the lady, who thanked me for reading and following the rules and making it easy on her, and then walked in. Once in, I emptied the two bottles into the bladder and tossed the empties in the trash. I had enough water to get me through the races without needing to pay the jacked up rates they have there.
Also, bring sunblock. Shade is a rare commodity out there and you will burn. Even worse when the weather is really nice because you don't think about it until it's too late.