Leaves produce carbohydrates through photosynthesis. They are not drawn from the soil. Adding carbohydrates to soil is to feed the bacteria in the soil which in turn, promote healthy roots.
If you want to give the plant more carbs, provide a good environment for it to produce them.
If you want to supply the soil with carbs, use molasses.
Why do you feel like you need to increase carbohydrates? I can honestly say I have never seen a carbohydrate deficiency