Hi Jessica,

Hope this will help you more or less. :)

Take Vitamin C tablets or eat fruits/vegetables rich in Vitamin C to aid your bodies natural defenses.  Hot Lemon & Honey or Blackcurrant both contain vitamin C and anti-viral properties and fresh ginger has natural anti-inflammatory properties - grate a little ginger and add it to hot water, sweeten with honey if required.

Be sure you keep your vocal folds moist and well lubricated. You can do this by drinking plenty of liquids throughout the day. Drink water rather than coke. Avoid iced water.

The air in airplanes is extremely dry. It is recommended that you avoid alcoholic, caffeinated beverages and drink at least 8 ounces of water per hour while flying.

Avoid Tea, coffee, cream, alcohol and spicy food. Keep tea and coffee consumption to a minimum though, as the caffeine in these drinks dries out the vocal folds and can make the voice sound raspy and scratchy. Alcohol is also bad for the voice, as it dehydrates the body and therefore the vocal fold.

Avoid excessive throat clearing & harsh coughing.

Avoid smoking and polluted air.

REST and relax.

And finally,
Good posture, correct breathing and proper breath support.

All the best!

Cheers
Jasper