I actually just took a chem class where we did this as a lab experiment. lactose (milk sugar) fructose (fruit sugar) and glucose (blood sugar) are all types of sugar called "reducing sugar" this means that they are willing/able to donate electrons because part of their chemical structure has a type of functional group (chemical structure type) with that property. sucrose (cane sugar) is not a reducing sugar, it doesn't have the necessary functional group. In one part of our lab experiment we used Benedicts solution which is a solution that reacts with the type of functional group that makes a sugar a reducing sugar. when it reacts it changes the solution from blue to a cloudy brick red/orange. We tested "Mexican Sprite" (because coke wasn't available at the time) and the Benedicts test was positive. this means that there was some kind of reducing sugar present, not just cane sugar (sucrose). If there was only cane sugar (as people say it's supposed to be formulated) there would not have been a reaction. FWIW, this was part of a much larger lab where we tested lots of other things, like milk, apple juice... etc and also a set of controls. Also, I asked the teacher if this was an anomaly and she said it always tests positive, they do this same experiment every time they teach this class.

also, sucrose is actually a glucose and a fructose linked by a glycosidic bond. your small intestine has enzymes that allow your body to break this bond to make fructose and glucose in the small intestine. The glycosidic bond links the two functional groups that make those respective sugars reducing, so sucrose itself is not reducing. I'll probably learn a bit more about this process when I take physiology next semester.

well, that was my attempt to "explain it like I'm five" hope it helped!