I’m not a nutritionist, but from my many years of experience with numerous diets and thousands of singers a pattern has emerged of which foods are beneficial and which are detrimental to the voice.
Any foods or beverages which stimulate phlegm (mucous) or stiffen muscles, particularly in the vocal folds, would be the ones to avoid for singers. Usually, dairy (milk, cheese, ice cream, etc.), very spicy food, citrus, bananas and anything you are allergic to such as gluten, are mucous producing. Stimulants such as caffeine or iced drinks will cause muscle constriction.
Your body needs energy so that it can perform for you. Help it to digest and metabolize well by keeping your food intake simple. I personally find juicy fruit and raw salads with a little light dressing to be easily digested by most people.
Add to that a small serving of pasta with tomato or garlic sauce (no cheese or cream sauces). If your body’s blood type does better with protein, then replace the pasta with chicken, fish or tofu with vegetables. I strongly advise against going hungry the day of a recording or performance. Hunger will stress-out your body which needs nutritional energy and hydration to deliver good vocal performance.
I’d love to hear from you which foods and beverages you have found have either helped or hindered your singing.