How to Make It
Combine water and sugar in a small saucepan and bring to a boil. Simmer for 3 minutes, until slightly reduced. Let cool, then pour into a medium pitcher.
Whisk in lemon juice, lime juice, sparkling water, and beer. Taste and adjust citrus juice level as needed.
Divide mixture between three 12 ounce beer glasses (such as a tulip glass). Garnish with a lemon or lime slice if desired. Serve immediately.