Never the healthiest of choices, eating a diet high in sugar is especially problematic during the flu because it causes inflammation. The last thing you need in already congested sinus passages is more inflammation. It will make it that much harder to expel mucus, which is the type of warm and moist environment that the flu virus loves. Inflammation can also weaken the body’s infection-killing white blood cells. So even though ginger ale is a traditional remedy for a queasy stomach, it’s best to stick to unsweetened ginger tea while you are ill.