Muddle the sugar. If you’re going the classic sugar cube route, add it to a lowball glass, top with the water and bitters, and use a muddler (or the end of a wooden spoon) to muddle and stir the mixture until the sugar is nearly dissolved.
Mix. Add the bourbon and a large ice cube. Stir vigorously for 10 seconds or until the liquid is chilled.
Garnish. Add a maraschino cherry or two, if desired. Gently twist the orange peel directly over the glass, in order to express its oil, then drop the orange peel into the glass.
Serve. Serve immediately and enjoy!