In a large bowl, combine daikon, carrots and jalapenos. In a saucepan, bring water, vinegar, sugar, salt and, if desired, liquid smoke to a boil. Simmer until sugar dissolves. Pour mixture over vegetables, ensuring vegetables are submerged; cool. Transfer to jars, if desired; cover tightly. Refrigerate, covered, at least 1 hour before serving. Store in the refrigerator up to 2 weeks, stirring occasionally.