Does ice cream help bronchitis?

Not directly: Interesting question. Airway inflammation can be helped with cool humidified air, like when an asthmatic goes outside and has some relief of their symptoms at night. I suppose if you're eating ice cream, some of the upper airway inflammation that may come with bronchitis may be relieved with just the direct contact with ice cream. Not sure i'd depend on it for a cure though.

No: Ice cream, although universally desired, has not been shown to provide definitive and reproducible benefit to bronchitis sufferers. On a related but somewhat different topic, although milk products have been implicated to worsen coughs, this is generally felt to be an old wive's tale.