Simple Syrup: Heat sugar and water in saucepan over low flame until sugar is completely dissolved. (Simple syrup can be stored in sealed container in refrigerator for up to 2 weeks.)
In a mixing glass, gently muddle mint leaves, vodka or gin, simple syrup and lemon juice. Add ice. Shake all ingredients well and, using a spring strainer, pour into a pint glass filled with fresh ice. Top with club soda and garnish with fresh mint leaves and lime wheels.