I popped into the middle of a conversation on the radio today. It was about the Dutch national football, about to play in the World Cup second round facing Mexico in Fortaleza. The conversation on the radio was about the heat (30+ C) and humidity (80%) at that location. These are tough conditions, but somehow they have a trick to minimize impact. It can freely be translated into "indrinking". What does "indrinking" mean in this context?
The term "pre-loading" may be closest to the idea expressed. This certainly applies if the same original Dutch word is used to describe drinking large amounts of alcohol before a party.
https://en.m.wikipedia.org/wiki/Pregaming - "Pregaming (also pre-drinking or pre-loading) is the process of getting drunk prior to going out socializing, typically done by college students and young adults in the United States and Europe, ..."
http://i.stuff.co.nz/national/health/69157335/Alcohol-pre-loading-has-party-goers-arriving-at-bars-drunk - a discussion of the phenomenon and its health effects.
I would guess that by "indrinken" he meant to drink enough so you wouldnt dehydrate too hard by the harsh weather