In an airtight container, mix coffee and water. Refrigerate for 12 hours.
1/3 cup ground coffee, 1/2 cups water
Strain coffee twice through a coffee filter or a fine-mesh strainer.
In a saucepan over medium heat, stir together water and sugar until dissolved. Bring to a simmer for 2-3 minutes. Remove from heat. Let cool entirely, then stir in vanilla. Store in an airtight container in the fridge for up to 1 month.
1 cup water, 1 cup sugar, 1 teaspoon vanilla extract
In a tall glass filled with ice, mix vanilla simple syrup and cold brew coffee. Top with club soda. Garnish with a straw.
1 ounce vanilla syrup, 1/2 cup cold brew coffee, 3-4 ounces club soda