In a small saucepan combine sugar, water, and the sliced jalapeno. Heat over medium-high heat for 5-6 minutes until the sugar is dissolved, stirring frequently. Reduce heat to low and let simmer for 10 minutes. Let cool. Leftover simple syrup will keep in the fridge for up to a month.
For the Paloma:
In a cocktail shaker with ice, combine tequila, grapefruit juice, lime juice, and simple syrup. Shake well to combine. Pour over a glass filled with ice, top with club soda and garnish with a fresh lime. Enjoy immediately.