Make the simple syrup: Place the cranberries in a medium saucepan with the water and sugar, stir to combine. Cook over medium heat and bring to a boil.
Reduce the heat to low and simmer uncovered until cranberries are falling apart, about 15 minutes.
Strain the syrup through a fine mesh strainer into a storage container. Discard the solids and let the syrup sit until cooled to room temperature (about 1 hour), then refrigerate the syrup for up to 2 weeks.
When ready to serve, fill a cocktail shaker with ice. Add the whiskey, lemon juice and the cranberry simple syrup. Shake for 30 seconds.
Fill a tumbler or highball glass with ice and top the ice with fresh cranberries. Strain the cocktail into the glass and serve immediately.
Cranberry Cinnamon Whiskey Sour by The Redhead Baker https://www.theredheadbaker.com/cranberry-cinnamon-whiskey-sour/