[Rory is studying on the couch as Lorelai walks into the room with two mugs]
LORELAI: Coffee and Ovaltine.
Ovaltine (originally Ovomaltine), a chocolate milk powder which can either be made into a hot or cold drink. It was developed in Switzerland in 1904, and quickly gained international appeal. By 1915 it was being manufactured in the US, among other countries. The drink is particularly popular in Britain, and the British version is also imported in the US.
It seems that Rory doesn’t have coffee before bed, the way Lorelai does. She may have trouble getting to sleep if she drinks coffee late at night, or the Ovaltine is a comforting childhood ritual.