I don’t drink alcohol. As a teatotaler, I find the substance an inexplicable waste of time and energy.
BUT– I agree it’s interesting to mix different liquids together in the pursuit of an interesting drink. I suppose its something like a "Junior Mad Scientist" in us that awakens sometime pre-adolescence. Or maybe we’re channeling Julia Child on a more manageable scale.
Anyway, I have no idea if there is a thread already started somewhere here on this but I figured what the heck, I’d post a couple of my favorite non-alcoholic concoctions.

Morning Blaster— I don’t drink coffee either. The various Golden-Girl-Cola descendants are my caffeine delivery systems of choice.
In this case, it’s a 50-50 blend of Orange Juice (preferably the new vitamin-stuffed Minute Maid) and Sun Drop/Mountain Dew/Mellow Yellow/store generic. The textures and citrus tastes combine nicely. You get your vitamins, minerals, and caffeine all in one package.

Night Blaster— I work skeleton shift at a Speedway. No matter how one controls one’s sleep schedule, about 3 a.m. the concentration starts to flag. My antidote is based on the things available at the soda and coffee dispensers.
Start with filling your cup 70% with Mountain Dew from the fountain dispenser.
Add a couple inches of Fanta Blue Raspberry from the frozen drink dispenser. The Fanta provided the cooling and the flavors combine to something akin to the Mountain Dew Baja Blast you can only get at Taco Bell. Finally, go over to the creamer section and look for Land o’ Lakes French Vanilla creamer. Add about half an inch of this to the cup. Some of the creamer will mix with the Fanta and make an interesting topping, while the rest will drop straight through and settle on the bottom. The overly strong French Vanilla will give the drink a stronger body and a flavor akin to cotton candy. Drink with a straw, stirring frequently. An hour later, you have the caffeine and sugar buzz needed to get through to the dawn.

And as a warning note, Things Never Meant to Be Mixed
–>Orange Juice and Cola. Really wretched, both in taste and appearance.
–>Milk and Cola. See above. More proof that Root Beer is superior to Cola.