In a small bowl, whisk together the sour cream, Greek yogurt, honey, and vanilla extract until smooth.
In a mixing bowl or salad bowl, combine the grapes, cashews, and dressing.
Toss until the fruit and nuts are well coated.
Notes
Store leftover grape salad in an airtight container in the fridge for 2-3 days. It will stay safe to eat for 5 days, but the grapes will likely become mushy.
I do not recommend freezing this recipe.
Feel free to use low-fat dairy, or replace the sour cream with yogurt for a healthier grape salad.