Can I replace icing sugar with corn syrup when I make the sponge cake? I don't have icing sugar and blender t blend sugar. So can I use what to replace icing sugar?
You can't make icing with syrup alone because it has too much water in it.
If you were planning to use the syrup in the cake itself you'd have to use more than the amount of sugar called for, and reduce the other liquid. All working by weight. Volume measurements here wouldn't work. But rather than trying to use syrup in the cake mix, it's better to use the finest white sugar you have. Many sponge cake recipes use caster sugar anyway, which is fine but not that fine.