"I do not drink warm beer."
Translation:Ik drink geen warm bier.
Yes and the Belgians know that to appreciate the flavours of their finest beers they shouldn't be cold. It is only people from hot countries with crap beer that would say something like this. If I went to a bar that pulled a bottle of trappist beer out of a fridge I wouldn't stay for a 2nd!
I guess it's about focus. With een/geen your focusing on what gets drunk. Thinking from German, I would assume that the usage of "niet" as well enforces the use of the definite article, e.g. "Ik drink het warme bier niet."
Afaik "geen" is aligned to "een":
Ik drink een warm bier.
Ik drink geen warm bier.