Dirty windshields are a fog hazard
The snorkel advice misses the root of the problem which is a windshield. This is a common problem and also extremely dangerous, especially for nighttime driving. A clean windshield is unlikely to fog up in normal conditions. However, a dirty windshield fogs up quickly and repeatedly until it is cleaned. Interior automotive glass gets contaminated especially quickly because there's so much stuff in the air to contaminate it. Anything you ever smell inside your car (new car smell, old car smell, exhaust fumes, McDonalds, Starbucks, bad breath) is also coating itself on the glass, and it doesn't take much of it to ruin the surface and make it prone to fogging up. Making things worse, ordinary Windex tends to smear dirt around more than pick it up. To thoroughly clean the glass you need a harsher cleanser. Try this: take a bottle of glass cleaner (ammonia + surfactant), add 10% rubbing alcohol (isopropanol) and 5% nail polish remover (acetone). On a warm day in the shade with the doors open, wear gloves, hold your breath, spray the solution on a crumpled newspaper and use that to clean the glass thoroughly. Repeat several times until the glass squeaks when you rub it. Getting the glass clean will definitely keep Wendy's windshield from fogging up, no matter how moist her husband's breath is.