From the Relays website, none of which has been superseded, I've bold-faced the most pertinent response to this question.
Aside from the items below, keep two points in mind: use common sense, and don't try to play word games on how big small can be.
I think the safest thing on food is to bring it in clear plastic bags and don't put those bags in a larger bag that's not clear. As for extra clothing in case the weather turns cold: wear it, then shed it.
= = = = = = = =
Please note, these guidelines will be strictly enforced:
*Backpacks and large bags (gym bags, duffel bags, etc.) WILL NOT be permitted into Franklin Field or the Relay Carnival Village for spectators.
*Participants (athletes, coaches, team medical personnel) WILL be permitted to bring in backpacks; these bags will be thoroughly checked, and will only be allowed in via the designated participant entrances.
*ALL bags containing food must be smaller than 12" x12" x 6" and in clear plastic bags. Sealed plastic water bottles and cardboard juice boxes are permitted inside the clear plastic bags.
*Coolers, glass bottles and cans WILL NOT be permitted.
*Animals are not permitted except service animals.
*Contraband items such as weapons, flag poles, sticks, and other poles are not permitted.
*Barbeque items and any open flames are not permitted.
*Smoking is not permitted in Franklin Field, per City of Philadelphia code.
*Penn Athletics is working with Penn’s Division of Public Safety which is responsible for the security of the event. The Division of Public Safety will have police and security personnel at every entrance (including athlete entrances) to thoroughly check and wand contents of bags and your person as you enter the Penn Relays.
*This procedure will take time, so please allow for ample time to get into the facility each day. This goes for athletes, as well; participants should plan ahead to ensure ample time to clerk for races.