So I looked it up. Turns out science doesn't really know what causes a hangover besides to much alcohol = hangover.
But there are a couple of researches that indicate that "Congeners" can make it feel worse. And these can get into drinks more if you use more ingredients. Therfore vodka for instance causes less hungover (though you're of course more likely to drink more alcohol when you drink vodka and therefore have a hangover anyway

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So the reinheitsgebot could help with this because they always have the same ingredients. Though I can imagine that your go to beer, grolsch for me and Jupiler for you, pretty much have the same Congeners all the time and you could probably get used to them. I also very rarely have hangovers when i just drink grolsch.