When I did it, we were given a pack of sandwiches, a small carton of orange juice, and a bottle of water. The 'usual functions' came courtesy of a tube fitting into a plastic bag containing a sponge - you hoped that nothing further was required. That was Goose Bay in Canada to Bruggen in Germany - 6 hours 10 mins according to my logbook. Boredom was the worst problem, followed by minutes of sheer panic trying to latch on to the tanker!!