This is a job for
Mighty Mug products!! I have used them on my cabin cruiser ever since they came out. They are the same diameter as any travel mug, so they fit in all cup holders. I linked the colored metal cups, but they also have stainless steel and plastic versions.
They have a proprietary "suction cup" space-age technology
that only releases if pulled straight up. So, they hold on a flat table for a listing ship at sea, or a vibrating motorhome wheeling down the road.