How to Make It
Stir together couscous and chicken broth in a medium bowl; cover and chill 8 hours.
Whisk together white wine vinegar, olive oil, sugar, salt, and pepper in a small bowl. Gently stir together chicken, tomatoes, onion, and herbs in a large bowl. Gently stir in vinegar mixture until thoroughly combined. Cover and chill until ready to serve.
To serve, fluff couscous with a fork. Spoon couscous onto a platter, and top with chicken mixture. Chill 15 to 30 minutes, and serve.