1On saucer or small plate, mix sugar and salt. Rub rim of chilled martini glass with 1 of the watermelon cubes to moisten; dip rim of glass in sugar mixture.
2In cocktail shaker with ice, shake vodka, watermelon juice, simple syrup and lime juice until blended. Pour into glass, straining out ice. Thread remaining 2 to 3 watermelon cubes on skewer or cocktail pick; add to glass.