Cut the vanilla beans down the center and scrape out the seeds using the back of a knife. Add the seeds and the pods themselves to a large saucepan.
To the saucepan, add the sugar and 2 cups water. Bring the mixture to a boil and let simmer for 5 minutes. Give the mixture a stir every now and again to break up the seeds.
Let this cool to room temperature, then refrigerate until ready to use.
The simple syrup will keep, covered in the refrigerator, for 3 weeks. (You can use this in iced coffee, or add sparkling water for vanilla soda. To that, add a splash of cream for a cream soda or a scoop of ice cream for a float!)
Add the freshly squeezed lemon juice to about 2 1/2 cups of the vanilla bean simple syrup along with the remaining 6 cups of water. Taste and adjust the lemonade to your liking.