Caffiene is a mild bronchodilator. That's why theophylline is still around because it is chemically related to caffiene, though I don't know how well it would work. An insanely large amount of caffiene would probably dispel a small inkling of tightness.

I find this interesting because I was once seen for a second opinion and the doctor required you drink Mountain Dew before spirometry to clear secretions. Funny, huh?