Van Gaal calls for water breaks
Temperatures are set to soar for the FIFA World Cup last-16 clash at Estadio Castelao and intense humidity is also a concern for Van Gaal.
The Netherlands coach has urged for common sense to allow his players to be allowed to take on plenty of fluid to avoid dehydration.
He said: "We hope that we get breaks to drink, otherwise we will put bottles around the pitch for the players,
"Dehydration is an element we have looked at in our training.
"Every people is different, but some can lose up to four kilos during the match, so you have to keep them hydrated as much as possible.
"We hope that the referee (Pedro Proenca) will referee in a sensible way."
The Netherlands won all three group games en route to the last 16, but Manchester United-bound Van Gaal expects Mexico to provide their toughest test.
He added: "I think Mexico is comparable to Chile (who Netherlands beat 2-0).
"The difference with Chile is that we could have been faced with two fantastic players (Arturo Vidal and Alexis Sanchez). Vidal didn't play so that was obviously a big advantage for us.
"But I think Mexico as an entire team is a better team. I believe that they play according to their qualities, their skills and they have great determination to win.
"For me, Mexico is the most determined team we've faced."