Jorge would have been referring to the use of sugars as a soil conditioner. Sugars can feed some microbes which do advance the breakdown of complex organic fertilisers i.e. manure, greenwaste, etc. This WOULD increase the availability of nitrogen to the plant- if you're using compost or other organics in soil.
The root membrane is the filter that permits or halts substances from entering the plant. Since sugar is not a required part of photosynthesis, it more than likely will not pass the root membrane.
Even if you could give a plant sugar through the roots, you'd have to give it the same sort of sugar that the plant itself makes. Sugars are not all the same- and there's numerous types. You can bet that your plant will not be interested in sucrose as contained in molasses or table sugar. Sucrose is a complex sugar with a long molecular chain, C12H22O11, as opposed to C6H12O6 (isomers glucose, fructose) as made by plants.