Combine the water, sugar, and vanilla beans in a saucepan and bring to a boil. Cook until the sugar has completely dissolved and begins to thicken slightly. Remove from heat and let cool.

Juice lemons until you have 1 1/2 cups of juice. Strain out pulp and seeds.

Add 3/4 of the sugar mixture to a large pitcher. Add lemon juice. Add water. Check for sweetness. Add more vanilla syrup if needed. Add berries. Let chill in the fridge for 2 hours before serving.

Pour over ice and garnish with more berries and lemon slices.