Fill a cocktail shaker with ice. Add the vodka, cranberry juice, lemon juice, orange juice and Simple Syrup to the shaker. Smash the slice of serrano chile with the back of a bar spoon several times and add it to the shaker. Shake for 8 to 10 seconds and strain into a cocktail glass. Garnish with the slice of jalapeno. This cocktail may be served straight up or on the rocks.
Put the sugar and water in a small saucepan. Cook over low heat, stirring, until the sugar dissolves. (Alternatively, heat in the microwave.) Store in a sealed container in the refrigerator.