different molecular makeup. i’m pretty sure it’s because natural sugar crystals have stronger bonds between the molecules/ atoms which means your body has to expend energy to break them up and digest them, while processed and artificial sugars have their molecules very available to our systems so they go right through and don’t require extra energy to be broken up. another knock on effect (?) is because as well as artificial sugars in those foods, you’ll usually find a lot of flavourings, “bad” fats, and and other processed stuff, but in natural sugary foods you’ll find fibre, phytonutrients, protein and other things that your body has to work for to break down :)