Meanwhile, snip the tomatoes into small clusters still attached to the vine. Place them on a baking tray and prick each tomato with the point of a knife. Drizzle with olive oil, sprinkle over the garlic, sugar and thyme, and season with salt and pepper. Drizzle with a little balsamic vinegar, then roast for 10–12 minutes, or until the tomatoes are blistered and tender.