Preheat the oven to 240°C.
Place the sweet potato batons in a large mixing bowl, and toss with the olive oil, sugar and a little salt. Place a wire rack on top of a large baking sheet, and arrange the sweet potatoes in a single layer. Bake for 15 minutes, then turn the sweet potatoes over.
Return to the oven and bake for a further 10-15 minutes until browned and crispy all over. Remove and allow to cool for a few minutes before seasoning with salt. Serve standing up in metal cups lined with nonstick baking paper.