Eating the right foods while you're sick can help aid in a speedy recovery. And, when you're feeling weak and a little out of it, proper nourishment is important for energy levels. Look for easily digestible foods that contain essential nutrients like protein, antioxidants, and vitamins. Probitotics, zinc, and vitamin C are especially helpful in shortening the length of colds and flu.
The exception to the above is if you're dealing with a stomach bug. In this case, it may be hard to keep food down so stick to easily digestible, bland carbs like crackers or toast. Clear liquids like chicken broth may be OK, and, when you feel a bit stronger, try eating a bit of plain yogurt, which can shorten a bug by almost two days.