Puree the 2 cups raspberries in a blender or food processor. Press the puree through a fine mesh strainer to separate the pulp from the seeds. Discard the seeds.
Combine the puree with 1/4 cup sugar in a small saucepan over medium high heat. Stir frequently and cook until mixture darkens and thickens, about 10 minutes. Chill until ready to use.
To make the cocktail:
Add 4 ounces vodka and 2 ounces amaretto to a shaker with ice and shake until very cold, about 20 seconds. Stir in 2 ounces orange juice and 6 ounces club soda. Pour into iced glasses.
Fill syringes with equal parts of the raspberry syrup and place in glasses before serving.
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Notes
This recipe makes four servings. To make for a crowd, you can increase the number of servings by changing the number in the "hover to scale" area of the recipe card. The cocktail portion can be made in a large pitcher for self-service and you can make as many syringes as needed.