Adding flavor to vodka I accept that one of the easiest ways to add flavor to vodka is simply to add a mixer or juice of some type, but that would be diluting it.  I also know that I can add fruits to the vodka itself which would infuse the vodka with a particular flavor.  Is there another way, say with some type of essential oil of some variety.  Overly sweet flavors should be avoided.
It's incredibly easy to infuse vodka with tea - unscrew the cap, force a teabag through the neck, screw the cap back on, and put it in the freezer until you're happy with it (overnight is fine). Keep the tag outside so it's easy to pull out. Tea vodka is tasty, and also makes a great base for cocktails.

You can also infuse it with horseradish, or ginger, or any other kind of root the same way that you would with a fruit peel - slice it thin, chuck it in, and give it a day. Unsweetened cranberries are great, and cranberry vodka is very popular in Russia and Finland.

With the right infusions, you can turn your vodka into gin.