If you're unable to drink your cup of coffee immediately after you've brewed and poured it, you're better off pouring yourself a new cup when you come back to it. Over time the flavors will fade, and you'll end up with something that tastes briny or burnt.
You can add a kick to your alcohol by adding your favorite liquor or liqueur. Beverages that blend well with coffee include Kahlua, rum, Irish whiskey, or bourbon. Fruit liqueurs also work well, and of course you should add a spritz of whipped cream, especially to Irish coffee.
If you're willing to drink decaffeinated coffee, don't expect it to taste quite like the real thing. Many decaffeinating methods use chemicals and processes that can change the flavor of the coffee. The best methods are European and Swiss water techniques.
