Why a drink can still tip at a berth
Container fit does not establish marine retention.
Motion changes the surface
Heel and wake can change the local slope even at a stop. A wider base does not eliminate those changes.
Keep the base supported
Do not straddle table hinges or gaps. The footprint is 5.2 inches across.
Use the appropriate travel arrangement
Before departure, use the vessel’s suitable holder or secure storage and a suitable drink closure.