(If you also have a sore mouth, sore gums, or a sore throat, talk to your doctor, nurse, or registered dietitian. They can suggest ways to help you without hurting the sore areas.) Choose and prepare foods that look and smell good to you.
1 Ravensara (R.aromatica) smells of a Cinnamon-Eucalyptus, and is also considered not as Therapeutic, but is used a lot for its Fragrance.  Ravintsara (Cinnamomum camphora) smells more of a Champhor-Eucalyptus, and is used when it is needed for Therapeutic purposes like respiratory help or shingles.
Thanks for the answer request. I'm not a vet so i don't really know. My guess is that what you're smelling are sulphurous compounds associated with garlic and onions. Perhaps review what your donkey is eating. Some vegetables such as cabbage and other Brassicas can cause gas and sulphurous smells in humans, perhaps donkeys too.