Turn cranberry sauce into a cheery adults-only drink.
In saucepan, simmer sugar, cranberry sauce, and 11/2 cups water, stirring often, until slightly thickened, about 5 minutes. Strain cranberry syrup; discard solids. Let cool. Fill 4 tall glasses with ice. Divide orange juice and tequila among glasses; stir. Slowly pour 1/4 cup cranberry syrup down inside of each glass so color sinks to bottom. Garnish glasses with orange slices and cranberries.