01 - Place frozen berries, lime juice, sweetener if using, and ice cubes into a high-powered blender.
02 - Pour White Claw hard seltzer and vodka into the blender.
03 - Blend on high speed until the mixture achieves a smooth, slushy texture.
04 - Taste and add additional syrup to adjust sweetness as desired. If the mixture is too thick, incorporate a splash more seltzer.
05 - Pour into chilled glasses and serve immediately, garnished with fresh fruit or lime wedge.