Combine water, lemon juice, lime juice and salt in a blender. Turn the blender on low and gradually increase the speed to medium. Sprinkle in the Methocel and Xanthan gum and shear in the blender for 30 seconds until the powders are full dispersed. Chill the mixture to 10 degrees Celsius. Stir in the simple syrup. The sour mix can be whipped to soft peaks using a stand mixer fitted with a whisk or an immersion blender with a whisk attachment.
Incorporate the whipped sour mix into your favorite drink recipe.