Line a cardboard box with a double layer of siliconised baking paper.
In a large pan, combine caster sugar, golden syrup, and water.
Dissolve the sugar over a gentle heat, stirring frequently.
Bring the mixture to a boil and let it boil for 10 minutes or until the temperature reaches 145°C.
Remove the pan from heat and quickly whisk in the bicarbonate of soda.
Pour the mixture into the prepared box and leave it to cool and set for 1-2 hours.
Lift the paper out of the box and peel away from the edges.
Use a sharp knife to break the honeycomb into chunks.