For the Clove Syrup, mix sugar and water in small saucepan. Bring to boil. Remove from heat. Add cloves. Let stand 10 minutes, stirring occasionally to dissolve sugar. Strain into small bowl. Cover and refrigerate until well chilled. (This makes 6 tablespoons Clove Syrup.)
For the Blackberry Syrup, bring berries, sugar and water to boil in medium heavy saucepan over medium-high heat, stirring until sugar is dissolved. Reduce heat to low; simmer, uncovered, about 30 minutes or until fruit is soft, stirring occasionally. Pour mixture through a fine-mesh sieve into a bowl, pressing gently on berries. Discard solids. Cover and refrigerate until well chilled. (This makes 2 cups Blackberry Syrup.)
For each pitcher of Blackberry Clove Spritzer, place 2 tablespoons Clove Syrup and 2/3 cup Blackberry Syrup in large pitcher. Pour 1 liter seltzer into pitcher; mix well. Pour into 5 beverage glasses. Garnish with blackberries. Repeat 2 more times with remaining ingredients to make 15 spritzers.