Line a baking sheet with a small-grate metal rack and then set aside. In a small saucepan, combine ½ cup of the sugar and water. Bring to a simmer, stirring until the sugar is dissolved.
Add the cranberries to the hot syrup, stirring to coat all the berries. Use a slotted spoon to lift the berries out of the syrup and place on the rack. Spread the berries out as best you can so they aren’t touching each other. Reserve 2 oz of the simple syrup to use in the cocktail.
For the rosemary sprigs, leave the top inch of leaves on each stem intact. Pull the remaining leaves off the stem. Dip the tops of the rosemary in the simple syrup and then lay on the rack.
Leave the cranberries and rosemary to dry at room temperature for 1 hour. They will still feel sticky and a bit tacky. After an hour, measure the remaining sugar into a bowl. Add the cranberries to the sugar, a few at a time, and toss to coat. The sugar will easily stick to the tacky berries. Roll the rosemary tops in the sugar to coat.
Transfer the sugared cranberries and rosemary to a parchment lined baking sheet. Let them sit for another hour so to fully dry and allow the sugar coating to set.
To prepare the garnish, carefully pierce a few sugared cranberries with the rosemary stems. If the stems are not sturdy, pierce the cranberries with a sharp toothpick and then thread onto the rosemary stems. Set aside until you’re ready to serve.