In a cocktail shaker, combine the orange and lemon juices, maple syrup, and egg white. Place lid on and shake vigorously for about 30 seconds to break up the egg.
Remove the shaker lid and add ice. Place lid on and shake again until the outside of the shaker is very cold, another 30 seconds or so.
Fill a serving glass with ice. Strain the contents of the shaker into the glass and top it off with sparkling water. Top it off with an orange slice.