I modified few things in your scene (disabled huge variance clamping, using NULL material for juice and couple of other details but none of them should matter for this topic)) just to be in "safe" start point:
The glass material cast a shadow as expected (i.e. because the lack of SDS paths). If I increase the sun size, making possible for eye paths to hit the sun disk, it starts to be possible to render SDS paths. The result using a HUGE sun disk is:
As expected, the juice isn't dark anymore but, indeed, it isn't the same scene. To recap, the software is working as expected (including not being able to render SDS in many cases).
I see only 2 solution to the topic problem:
1) being able to render SDS paths.
2) use some kind of fake to work around the problem.
In both cases, I'm not going to look in any new feature until after the release of v2.2 so we will have to wait before we have general solution to this problem.
For more details about #2 check my next post.