Excellent sources are fresh fruit and vegetables. Particularly generous are avocados, a variety of nuts, seeds, sweet corn, olives and cold pressed oils. Avoid Sugar and artificial sweeteners. Aspartame, found in artificial sweeteners, is detrimental to the entire hormonal system, of which the adrenal glands are a part. Refined sugar, in all its hidden forms, is also very taxing on the hormonal system.
Caffeine artificially stimulates the adrenal glands, which is fine and well occasionally.
But bear in mind that caffeine is like a stick to the donkey. The adrenal glands will tire eventually and only respond to more whipping. Rather treat them with the carrot for good results. Animal fats as they can prevent the body absorbing EFAs, necessary to the adrenal glands as described above. Artificial chemicals are foreign to the body, confusing it, so it may not even recognise them as something to be eliminated.