- Place the watermelon in a blender and blend until pureed and liquified. Pour the contents through a fine mesh sieve, saving all the watermelon juice in a large pitcher.
- Add the sugar, water, ginger and vanilla beans plus the empty pod to a small saucepan. Heat over medium heat while whisking constantly until the sugar dissolves. Allow the mixture to simmer until it becomes syrupy (ours took about 20 min.). Remove from the heat and let cool.
- To assemble the drinks, add crushed ice in a cup. Pour a few ounces of the vanilla ginger syrup into the cup, then add 4 or so ounces of watermelon juice.
- Add about 2 ounces of club soda. Taste and adjust the drink to your desired taste – more syrup or juice, or more club soda. Stir well to mix. Serve!