Combine cranberries, orange juice, sugar, and ginger in a medium pan over medium-high heat; bring to a boil. Continue to boil until cranberries begin to pop. Once cranberries have popped open and softened, use the back of a wooden spoon to smash them against the side of the pan. Remove from heat and cool.
Strain cooled cranberry mixture into a bowl through a fine mesh sieve. Discard solids and refrigerate juice until chilled, about an hour. Transfer juice to pitcher and stir in sparkling water. Serve with cranberries or orange slices as garnish, if desired.
Total time doesn't include time needed to chill cranberry mixture.