Take the cut lime and cut again in quarters. In each glass, muddle (mash) 4 pieces of lime, sugar and about 7 to 10 mint sprigs and mix well. Repeat process with second glass. Add ice. Pour tequila to each glass. Divide watermelon juice into both glasses and splash some club soda (or to taste) to each glass. Garnish with lime wedges and mint sprigs. Enjoy!