Combine sugar, vinegar, salt, ginger, and red pepper flake in a small saucepan. Bring to a boil over medium-high heat, stirring to dissolve sugar and salt. Remove from heat and let steep for 5 minutes.
In a medium bowl, combine cabbage, carrots, sesame seeds, and peanuts. Strain vinegar mixture over the top and stir.
Add sesame oil and tamari sauce, stir to coat. Cover and refrigerate for at least an hour before serving.