As somebody who regularly employs developers, and being a developer myself, may I suggest you put your Saturdays' effort into an open source github repo or something similar? Sure, this takes time too, but afterwards you can just point your prospective employer to your superbly styled and documented code on github. Both parties win: you don't have to spend time on stupid exercises anymore, they can get a very decent impression of your coding skills.
I was thinking about posting some of the solutions to past problems on github. The problem is that new employer has no way of knowing it was me alone that provided the solution and how long it took, so I couldn't blame them for not just accepting my public repo as proof of my ability.
For example I had one interview where I struggled to complete a WPF test project simply because it was coded in a way i've never done before using controls I've never used and the test was estimated to take 10 min. Meanwhile in my bag on my laptop I had a complex WPF solution i've been working on in my free time for months as a possible product to market and sell which more than showed my competence in the platform. People in my interview didn't even want to see it on pretext that they have no way of knowing it's my code.
[Edit: corrected typo]