I've been looking into this question and it seems hard scientific research has given us some leads.
Tyrosine is an amino acid thought to promote creativity. Foods with the highest levels include spirulina seaweed, egg whites, salmon, and lowfat cottage cheese.
Alcohol boosts creativity by blocking analytic "working memory" for the benefit of creative problem solving.
Dark Chocolate boosts the brain's blood circulation for about 3 hours while the caffeine in Coffee/Tea keeps you alert for a couple hours.
Complex carbohydrates provide the brain a steady stream of glucose throughout the day, for example,
whole grain bread, quinoa, oats, and brown rice.
Antioxidants keep the brain oxygen flowing. For example, berries, kale, and broccoli.
The smell of cinnamon-vanilla is said to enhance creativity.
Foods that Inhibit Creativity
Junk Foods with Simple Carbos (store-bought cookies, oreos, etc.)
Foods High in Sugars
List of Foods/Drinks in the Writer's Diet
Lowfat Cottage Cheese