Here's a simple device to secure those water bottles, cokes and beers that flop out of your four inch drink holder. I think it's called reducer and can be found in the appliance section (drier vents area) at Home Depot for about $2 (pic #1).
It measures 3 15/16 " across at the larger end and should jam right in to the drink holder (pic #2). The inside diameter in the small side is about 3 1/16". Works great for most drinks!
If it's slightly too big or you want to create a slight taper to go deeper in the hole, you can cut a couple of slots in the base (shown upside down in pic #3).
Want to keep it flush to the deck, trim off some of the top and voila (pic #4)!
So use it off the shelf or customize it; this works in any of the 4" drink holders, such as the Adventure (pictured), Revolution, and ? Stow it in the hatch when not in use.