Alcohol Okay, it’s not a food, but you should still avoid this beverage. That beer or vodka tonic may hit the spot, but it’s also dehydrating. Unfortunately, the air we breathe in planes isn’t humidified, which also causes flyers to become dehydrated. Throw alcohol into the mix and you may be more relaxed, but you’ll come off the flight feeling parched and miserable. And keep in mind that alcohol has a bigger effect on your body at higher altitudes!