I don't know what vitrargo is, what does it contain?
I have not tried to rehydrate before a fight, but I have read a few things about loading up with water. Two ways might help (don't do this the first time for a fight, try it before in case you get bloated or don't rehydrate at all).
First is drinking glycerin, at least I think thats what it is. I used to sell it at GNC and nobody would buy it because nobody knew what it was. It was meant to hydrate you more than not taking it. You would mix a certain amount in water or a shake and drink that instead of the shake itself. It was supposed to promote water retention and hydration. I only tried it a few times, and it did seem to work for me. I didn't urinate that much and I seemed to be less thirsty than normal. A study showed that in one marathon in Mexico 3 elite athletes used it and 2 didn't. The weather was incredibly hot, and the 3 that took it were the only ones that finished the race.
Lastly is bicarbonate loading. You mix sodium bicarbonate in water and drink that. It is supposed to promote more water retention than water alone. If you google it you can find instructions and tables showing how much to add and how much to drink.
I would assume this would help, but I have never tried it or heard of anybody trying it for a fight. I think it is more popular in endurance sports and have heard of runners and soccer players using it.