You enjoy the taste of dark, milk or white chocolate bar, both the sweet, semi-sweet, bittersweet one and so on and you are not certain if you can give your rabbit a little bit of it or it will be harmful.
Chocolates are very nutritious and have fiber, minerals such as iron, magnesium, copper, manganese, potassium, zinc, phosphorus, selenium, vitamins including A, K, thiamin, riboflavin, B6, B12, carbohydrates, fats, proteins which are all an essential part of a rabbit’s nutritional requirement.
Therefore, can I give my bunny a piece of the sweet confectionary or should I not?
Can bunnies eat chocolate?
No. Rabbits should not eat chocolate. Like in the case of dogs, this “sweet treat can be poisonous to rabbits and should never be fed to them.”  This confectionery has methylxanthines which contain caffeine and theobromine. Theobromine is toxic or poisonous to rabbits. 
If a bunny ingests theobromine, clinical signs will be expected after 4-24 hours and theobromine mainly affect the heart, kidney and nervous system.
Depending on the amount ingested, symptoms “include vomiting, diarrhea, restlessness, rapid breathing, incoordination, increased heart rate, seizures and in some cases the animal might die 
Do rabbits eat chocolate if given? Yes. They will eat it. In fact, they will enjoy eating it without knowing the possible consequences. Bunnies, like human beings, have a sweet tooth for sugary things. Therefore, avoid giving them this confectionary and do not assume they will not like it.
It is high in carbs
Besides the toxins, rabbits depend on high-fiber, low-energy foods such as grass hay. Their hindgut digestive system is adapted to handle such foods as they also help in gut motility. This is your bunnies need an unlimited supply of grassy hays such as Small Pet Select 2nd Cutting "Perfect Blend" Timothy Hay Pet Food or Kaytee Timothy Hay
Therefore, foods high in sugars and carbs will affect your pet’s microflora balance by encouraging the growth of the harmful bacteria leading to enteritis, diarrhea, bloating, among others.
Always, avoid any food that has high amounts of carbs and low amounts of fibers including grains, nuts, bread, and so on.
What should I do if my bunny eats chocolate?
If your bunny ate this confectionary, you need to immediately contact your veterinarian. The effects it can cause will depend on the concentration and amount. Let your vet know which type of chocolate it was and the amount ingested.
During diagnosis, there might be bloodwork as well as ECG if they suspect arrhythmias (irregular or abnormal heartbeat rhythm).
There is no antidote and treatments will include medications to control blood pressure, seizures, heart rate, intravenous fluids and any other treatment that your vet may find fit including removing the remaining chocolate in the stomach using a tube.
Rabbits should never be given chocolate candy bar, mint, cakes, cookie chips, or any other confectionery that has chocolate ( since it has theobromine) or any other product with this substance including cocoa powder, dry pudding packs, Instant Breakfast, candy, kola nuts, Guarana, among others.