Avoid it. A void feeding anything with simple sugars (such as molasses) and avoid feeding starchy foods that the body converts to sugar (bread).
Sugar can be a big problem in rabbits. Excess sugar can lead to GI stasis or cecal dysbiosis and either condition can result in dehydration and possibly death to the rabbit. The yeast in the Chaffhaye will feed on the sugar (Molasses) and result in a large yeast overgrowth that can destroy all the good bacteria (the much needed gut flora and intestinal biota) which will lead to serious problems – possibly death.
A small treat now and again isn't likely to hurt, but you should avoid feeding anything sugary on a regular basis.
Chaffhaye is designed for horses, which process sugar very differently than a lagomorph (rabbit).