Sugar water is used to get a similar osmotic pressure as nute water, but without the nutrients. I'm not saying this is needed, but the idea is that if you use pure water, it will cause a surge of water to flow into the buds due to the osmotic gradient created by the pure water flowing into the buds. The gradient is caused by the low levels of dissolved stuff in the reservoir vs the relatively high amount of potassium in the plant tissue. The steeper this gradient, the higher the water pressure will be.
I've also heard of people adding too much clearex and having the plant shrivel up, since too much sugar will cause water to be sucked out of the plant.
The idea is that clearex (sugar water) is supposed to be an isotonic solution so the cells don't burst or shrink.
I'm not sure how much bud bursting really matters, but tomatoes or other soft fruits, maybe this type of product has more relevance.