I don't think that loading yourself with liquid a week before raceday is the thing to do. I am not convinced that hydrating any time before the day of the race will make any measurable difference.
But note that "any liquid will be fine" is actually not good advice. Because some will DEHYDRATE you.
You already implied that alcohol is bad... quite apart from the toxins, almost everybody knows that your body uses up water in trying to get rid of alcohol and the other toxins... hence the dehydration and thirst the next morning.
But also some people believe that coffee, tea, coca cola, Red Bull and any caffeine containing drink has a diuretic effect. The same with herbal teas. A good illustration is herbal teas containing dandelion.... but other herbs can do similar. You remember how when you were a kid, people used to say that if you picked dandelions, then you'd wet the bed... well that's because of a duretic effect.. making you urinate more. (The french word for dandelion is 'pissenlit', which literally translates to 'piss in the bed'). Personally, I believe that drinking a lot of tea has a diuretic effect, but there is some debate about this.
Pineapple juice also has diuretic effects - and strawberries.... indeed I understand that dried pineapple is sometime used as a natural remedy where somebody has a water-retention problem. It has a dehydrating effect. So choosing what you eat, as well as drink is important could have a small effect on your hydration and performance.
For me, if I run say 10 miles, I believe that if I take a 30-40 second 'break' to take on water half way through, then I more than make up that time by improved performance in the next few miles. It is also healthier.
On an important, but somewhat unrelated issue, there is a body of opinion that what you do day to day (drink little), is not good for your health. You should take on extra water, even if it costs you an extra couple of trips to the loo each day. In layman's terms, by not drinking enough, your blood (and other bodily fluids) are enriched in natural toxins. Some people believe that not hydrating enough is as bad for your cardio-vascular system as having high cholestrol.
In summary, I'd recommend not bothering too much about over-hydrating a week in advance... but in the last few hours before the race then, yes. You might as well start with decent hydration so increase your water intake somewhat... and watch out for drinks and food that could undo some of that good work by causing you to lose the water you're taking on board.