Use this thinner, chocolatey syrup to make an egg cream, chocolate milk, or milk shakes.
Combine sugar, corn syrup, and 1/4 cup hot water in a saucepan; bring to a boil over medium-high heat. Reduce to a simmer; cook until sugar dissolves, about 1 minute. Remove from heat; stir in chocolate until smooth. Stir in vanilla and 1/4 cup warm water. Serve (or store in an airtight container, refrigerated, up to a week; warm before serving).