Simmer cranberries with ginger. Combine cranberries, water, and ginger slices in a small pot. Bring to a simmer for 7-10 minutes.
Crush the berries. Use the back of a spoon to mash cranberries as they soften, helping release their juice.
Strain the mixture. Pour through a fine mesh strainer into a bowl, then add fresh orange juice through the same strainer.
Press to extract juice. Use a spoon to press on solids, extracting every bit of flavor from the cranberries and ginger.
Add sweetener. Stir maple syrup into the warm liquid until dissolved completely.
Chill thoroughly. Cover the syrup and refrigerate until cold, at least 1 hour or up to 4 days.
Build each drink. Add ice and a few fresh cranberries to glasses, then pour in 3-4 tablespoons of syrup.
Top with bubbles. Fill each glass with chilled sparkling water, stir gently, and serve immediately.