This is what I bought for holding my coffee:
Porsche Cup Holder
I mounted it on the passenger side of the center console. It seems to work OK. Not too far to reach...I don't even take my eyes off the road. I'm not sure where you'd mount it in an SC, though.
I also used to have a coffee cup that had a flared bottom that seemed to handle most normal driving w/o tipping over. Don't know where you'd find one now, but it probably would do a good job when set on the floor.
Regards,
Jim
1995 Black 993 Coupe