At buffets, a drink will almost certainly be included at no charge (since the under 3's eat for free at buffets anyway). At regular, order-off-the-menu TS restaurants, like katieelder said, I'd be prepared to pay, but not surprised if they give you a free beverage at least some of the time. At CS restaurants, you'll almost certainly have to pay--I'd be very surprised to get a free milk or juice.