1. Preheat grill to medium-high heat.
2. Arrange bread on grill rack; grill 1 minute on each side or until well marked. Cool slightly; tear into chunks. Combine bread and tomatoes in a large bowl.
3. Combine oil, vinegar, and sugar in a small bowl, stirring until sugar dissolves. Drizzle over bread mixture; sprinkle with salt and pepper. Toss gently to coat. Sprinkle with basil leaves.