MB GL450 has a net bottle holder (looks like a mini cargo net) near the left foot of the passenger, up against the center dash wall. You can buy it online and taking 2 small screws screw it in. You know have a bottle holder (BTW: In MB world - that's what its called).
Here's the link: http://www.ebay.com/itm/2000-2006-M...ash=item51dd7b5298:g:qiIAAOSw37tV-jMm&vxp=mtr
Here's the link: http://www.ebay.com/itm/2000-2006-M...ash=item51dd7b5298:g:qiIAAOSw37tV-jMm&vxp=mtr