Try staples!!!! :hilarious
Sorry, coffee not kicked in yet.
I don't have problems as long as the glass stays nice and clean. I usually clean the suction cups really well too before putting them on. One trick I have tried with good success is to put a TINY dab of corn oil on the suction side before putting it on. This helps keep water out and provides a real good seal. The oil is organic so it won't harm the system. Just enough oil on your fingertip to provide a slight glaze to the cup is all you need.
You could also try duct tape!! :hilarious OK, time to get another cup of coffee!!