For Coke Syrup:
1. Make syrup by bringing Coca Cola and sugar to a boil on high. Boil until reduced to 1/2 cup, about 20 min. Let cool.
2. Into a shaker, add .75oz Coke syrup, rum, lime juice and egg white. Cover and shake for 10 seconds without ice (dry shake).
3. Add a generous amount of cubed ice to the shaker and again shake vigorously.
4. Strain into a rocks glass over cubed ice and serve.