I assume you are referring to some type of product designed to add carbohydrates? Brix(sugar)levels, can be monitored in the plant to detect stress, as these levels drop before there are actual visual signs. Carbohydrates are important in all natural grows as exudates are exchanged between the plant and micro organisms(nutrient exchange). I add carbs in my grows by different methods, the main one being unsulfured molasses used when "brewing" microbial extracts. Keep it Green! Peace!
In all natural grows they are of major importance as this is the main food source of most bacteria. Peace!
Watch pH if your not going to aerate for a day or 2. In my experience molasses drops pH way down, I use earth juice hi-brix love it but would only recommend if using organics or making teas. I started out using it with hydro nutes and it would drop pH to below 4 and was incredibly hard to raise back up. I just started to use it again recently when I switched to using earth juice products and aerating for a couple days, haven't had any problems since. If not using organics I'd recommend sugar daddy, its a little pricey but its a more soluble form of molasses and doesn't affect pH as dramatically...