preparing coffee as is making is the preffered expression
It is an American usage, and fairly common. This discussion list TV usage, for example. https://forum.wordreference.com/threads/fix-breakfast-dinner-meal.2441925/
Well, her argument was that while it sounds perfectly fine with breakfast, dinner or even soup, she has never heard it with beverages, apart from 'fix someone a drink'... And this link seems to only mention meals.
I've spent almost two years dealing with this forum and I don't remember anyone before you suggesting "fix" in such sentences, even those with breakfast or dinner.