Bring 2 1/2 cups of water to a boil. Stir in the couscous, cover, turn off the heat, and let stand for 5 minutes. Transfer couscous to a wide, shallow dish. Fluff with a fork to separate the grains, and then cool to room temperature. Combine the oil, lemon juice, basil, garlic and sugar in a salad bowl. Add the couscous and remaining ingredients and toss to combine. Cover and refrigerate until ready to serve.