Hello Meoman. Blood sugar isn't blood sugar, it's blood glucose, to be more precise. I'd suggest ignoring what the nutritional analysis on food packaging says about sugar: just look at the total carb figure (assuming you're in the UK; in the US you would look at the net carb figure).
Actually the digestive system disassembles (some) disaccharides and polydisaccharides. Whilst in theory it is possible to change fructose or galactose into glucose (or glucose into galactose) it turns out to be easier for the human body to make sugars from other organic compounds. It would also be pointless since human cells are perfectly capable of using fructose or galactose for respiration. Assuming that the liver let these sugars enter the general blood flow. (Typically the vast majority of dietary fructose and galactose is converted to fat by the liver.)
Glucose tends to be the most common sugar in most people's diets in practice.
A product containing white flour would probably spike your blood glucose more than a spoonful of sugar.
The flour is mostly glucose (amylose and amylopectin), whereas "sugar" (sucrose) is only half glucose. Also α-amylase is present in human saliva whereas sucrase is produced in the small intestine. So the flour will be hydrolised before the sugar in any case.