While homemade is probably better, I usually just buy bottled gluhwein. The Sternthaler Nurnberger Christkindles Gluhwein costs about $7 for a 1 liter bottle, and it tastes exactly like what they serve at every Weihnachtsmarkt I've ever been to in Germany. Although of course there's no substitute for being outside at a Weihnachtsmarkt with a steaming gluhwein, halb meter bratwurst, and kartoffelpuffer mit preiselbeeren!