No food/drink is allowed inside the test room. You can consume them in your break time. Technically you could come out during the test for a break but the time will not be stopped on the test. So you would lose time if you do so.

Generally protein rich food is better. Avoid caffenine drinks and avoid too much liquids just before or during the test.

Here is what I have been preparing for my practice CATs.

Proteing shake: 1 cup of water, 1 cup of milk, 1 scoop (about 24 grams of protein) chocolate-flavored casein powder (a slowly releasing protein), a cup of strawberries, a full tea spoon of natural peanut butter (slows down digestion of the shake) all blended together. I prepare two of these shakes for the two breaks. Liquid food is easily digested and can be quickly consumed, which is an ideal combination when you have just 5 minutes.

AND

A "Chewy" granola bar from Quaker, which is delicious.

You can get the protein powder from any Vitamin Shoppe store or online from eBay.

You can get your natural peanut butter from any supermarket (I prefer Trader Joe's peanut butter).

All of the other items can be purchased at your local grocery store.

Walgreens has excellent sales on the Quaker bars.

Make sure that you include MILK along with the water. Milk holds water well, which reduces your chances of thinking about your bladder rather than the test material midway through one of the sections.