Those were actually one of my horses favorite treats.
Lots of sugar and carbs, so not the best thing for a rabbit to be given though. Could lead to disrupting the normal microflora in the gut and cause mushy poop(or possibly more serious digestive illness) if too much gets eaten. But shouldn't be harmful if he manages to steal a tiny crumb, if he's not sensitive to digestive issues. Think of it as the treat category, no more than a very tiny amount should be allowed in a day. Fresh fruit would be a better treat though(small amount per day, properly introduced, gradually to avoid digestive upset), but only for rabbits not prone to it causing digestive upset.