Ultimate Cupholder
The stock cup holders in most BMWs are useless and I couldn't find
an after-market cup holder that worked well and wasn't way over-priced,
so finally I designed one myself. It's a nicer version of one that I
made a long time ago. I've used it in all three of the BMWs that I've
owned (E34, E36, and E39). It's the best approach for a practical cup
holder that I've found yet for the 5 Series cars.
It's a simple, one-piece, all-metal design,
made from 20 guage 304-grade stainless steel. It's large enough to actually
be useful in the real world. Unlike the stock cupholders, it's basically
indestructable - no moving parts or little plastic pieces to break.
I tried a number of more complex approaches, but, as in the case of
many things, the most simple seems to work best. (It's a cup holder
- how complicated does it need to be?)
It fits under the edge of the center console
as shown in the picture below.

Installation and removal are easy - it just
slips in and out. Requires no alteration at all to the car.
I think this is the optimal location in these cars as opposed to others
that mount along the center console or armrest areas. Here it's out
of the way and inconspicuous, but still easily accessible. It's the
only the ONLY spot that I've found that doesn't take any useable space
or restrict any typical functions of the car. Also, if a spill does
happen, it will be on your mats, not on any person or electronics. It
works on both the driver's and passenger's sides in this same location.
Works great. Holds anything from 12 oz.
cans, to one-liter bottles. Stands up to just about anything that you
can throw at it short of rolling the car without spilling. No more reaching
over to hold/catch things when cranking through a hard turn!

More examples are shown here.
The holder is sized to fit most standard
drink containers. The arms can be bent out or in to better fit anything
larger or smaller. The curves of the arms naturally accept containers,
and the height and span are optimally sized to hold the widest possible
range of items. Basically, you can just drop things into it, and they'll
stay put. Smaller containers like cans fit more loosely, but they will
NOT spill (within reason at least). The felt lining prevents any rattles.
The center of gravity and holding force are down low where they need
to be to keep things in place. Also provides for improved safety in
the event of an accident since containers are less likely to launch.
I have these CNC cut by laser, and then
form and finish them by hand. Even though you don't really see them
much in use, I wanted something that looked nice enough to put into
the cars. I think it came out pretty well. If interested, you can get
one here: BMW
cup holders at http://www.ultimatecupholders.com. They also work
with Porsche, Mercedes, Audi, Acura NSX and other cars with a similar
console arrangement.
And, yeah I know I have way too much time
on my hands... thanks. ; )