Yes, it is sugary, but in moderation doesn't hurt your horse. Its only about 55% sugar. Also sugar in little amounts is good for the horses digestive system.
That's funny - My horse who ties up is on a completely grain and sugar free diet, and one teaspoon sets him off.
It's your choice wether to feed it or not, but it is NOT
good for horses, and the slight nutritional value it may have can easily be made up by feeding a good vit/min supplement.