Well I feel that 100kg of water because it's dead weight over the trailer wheels. (Prado V6's are not known for their stump pulling torque LOL)
In my experience with sand driving anything you can do to lighten the load over a non-driving axle like on a trailer is worth it.
When I built my rig and set up the Kitchen/chairs/ etc insides, if I could get it in alloy or plastic I got it (with the exception of cutlery!)
Rule of thumb, when setting up for a run on the sand I'd re-arrange things and increase the ball weight by about 25kg so that would transfer weight to the car's driving wheels, and take a proportionate amount of weight of the trailer axle.
So I've decreased my dead weight by:
Water- 100kg
Ball weight- 25kg
getting lighter stuff, leaving behind un-necessary stuff- 40-50?
?
There's also the option to swapping some of the heavier items in the trailer for lighter items that are normally in the car on a road trip.
So it all adds up
I say this because sand driving can be unpredictable, and as some other posters will say, even in good conditions it only takes some other clown who will cause you to have to stop or go off line and that's when this kind of preparation is a big help in the difference between getting stuck or pulling through.