This is, of course, the last resort when you find yourself in some shit that you never expected to find yourself in and you have no motion sickness medication whatsoever, nobody who can lend you some, and no way to buy some in time.
This is a simple tried and true technique that works for small bumpy roads and obstacles but of course not full blown wavy boat rides.
You find a spot on the wall or on whatever is front of you and you don’t take your eyes off it until the ride is over. You don’t turn your head even slightly when someone calls your name. You don’t look at the Great White Shark that just ate a passenger who fell overboard. You just look at that same spot until everything stops, because if you turn slightly, it’s all over. Blowing chunks.