Line the base and sides of a 30 × 20 × 3 cm (12 × 8 × 1¼ inch) tray with baking paper.
Place the sugar, glucose and 20 ml (⅔ fl oz) water in a small saucepan and heat to 167°C (333°F), without stirring. Remove from the heat, add the bicarbonate of soda and stir to combine. Pour onto the tray and allow to harden. Break into 2–3 cm (¾–1¼ inch) squares.