At the four major parks (AK, DHS, EC, MK) coolers are restricted to "small, soft-sided, which can fit in a locker". And they cannot be rolling bags.
The only restrictions that apply to all parks (theme and water) are nothing in glass containers (other than medicines and baby food) and no alcoholic beverages.
Some things people don't think about (which tend to be in glass) are pickles, salsa, Mayonnaise, Starbucks drinks, Snapple drinks, Tabasco.
At the water parks any type or size cooler is acceptable. I have seen people come through the gate (Typhoon Lagoon) hauling wheeled coolers about 4' x 3' x 2½'. Note that the cooler can be on two wheels or carried, but the way the rules are written you can not have it in a wagon and it cannot have four wheels.
If you show up at the gate with prohibited items we will give you three choices:
(1) Take prohibited items back to your car or resort.
(2) Put prohibited items in the nearby trash can.
(3) (Only for other than alcoholic beverages) If you have plastic bags or cups you can dump the items out of the glass containers and throw away the container.
