To make the sweet basil syrup, add sugar, water and regular basil to a small saucepan, and warm over medium heat. Bring mixture to a boil, stirring until the sugar dissolves. Take the saucepan off the heat, cover and let infuse/cool for 30 minutes. Pour the syrup through a strainer into a clean container. Store the sweet basil syrup in the refrigerator for up to a month or two.

To make the Summer Crush cocktail, add sweet basil syrup to a cocktail shaker with the Thai basil, heirloom tomato and watermelon. Using a muddler (or the back of a wooden spoon), muddle these ingredients together. You want to bruise the basil, and release the juices from the tomato and watermelon.

Add vodka, lime juice and ice to the cocktail shaker, secure the lid, and shake until the drink is mixed and well-chilled. Taste a little bit of the drink, and add more sweet basil syrup or lime juice to taste. Pour the drink through a fine-mesh basket strainer into a short tumbler filled with ice. Discard solids. Garnish the glass with a wedge of lime.