Water, whole leaf gunpowder green tea, wine, whisky and the occasional beer are my fluids of choice.
Rather than cola, i prefer a sparkling water, mineral or otherwise, with some lime. I used to drink a can or two of diet coke, but now the flavor is strangely chemical to my taste buds.
Tea, in moderation, is a superb choice. Dig this, even: Tea 'healthier' drink than water