In a large saucepan, bring the water, 1 cup sugar and vanilla to a simmer stirring until dissolved.
Turn off the heat and add the cranberries tossing with a wooden spoon to coat. Allow the cranberries to sit in the simple syrup for 5 minutes and then transfer to a wire rack.
Allow the cranberries to dry for 20-30 minutes.
Pour some sugar in a shallow dish and roll the cranberries in the sugar to coat completely.
Transfer to a baking sheet lined with parchment and allow to dry completely, approximately 1 hour.
Store in an airtight container for up to 48 hours.
Notes
Fresh Cranberries: Use firm, fresh cranberries for the best texture. Frozen cranberries are not recommended because they can release excess moisture when thawed.
Sugar: Regular granulated sugar creates the classic sparkling coating. Use enough additional sugar to coat the berries evenly.
Drying: Let the cranberries rest for 20–30 minutes after removing them from the syrup, until they're sticky. After rolling in sugar, dry for approximately 1 hour or until the coating has set completely.
Make Ahead: Prepare up to 2 days in advance for the best appearance.
Storage: Allow the cranberries to dry completely before placing them in a covered container. Store in a cool, dry place for up to 48 hours.
Troubleshooting: If the sugar coating becomes damp, gently roll the cranberries in a little fresh granulated sugar.
Freezing: Not recommended. Moisture from thawing can cause the sugar coating to dissolve.
Variations: Vanilla can be omitted for a traditional version. Orange zest, cinnamon, or rosemary may be used to flavor the syrup.