Make the cinnamon simple syrup first.
Mix water and sugar in a small saucepan. Add cinnamon sticks and bring to a boil.
Reduce the heat and simmer for 10 minutes.
Remove from heat and let it cool. Take out the cinnamon sticks.
Fill the cocktail shaker with ice.
Add whiskey, apple cider, cinnamon simple syrup, and lemon juice.
Shake well for 15-20 seconds until the shaker feels cold.
Strain the mixture into a rocks glass filled with fresh ice.
Garnish with an apple slice and cinnamon stick.