When driving (a car) there are occasions when I need to convey “thank you” to other drivers (for letting me merge, for stopping at the side between two parked cars to let me pass in the opposite direction on a narrow street, etc.)
On other occasions I need to signal “sorry” (when I misjudged and someone with right of way has to slow down).
Now for “thank you” there is (at least in my region of Germany) a reasonably standard driver’s gesture of holding one hand up, open. It is practical in that you can also use it to a driver behind you, but it also can be confused with a greeting wave.
For “sorry” I have not found any fitting gesture. I try to radiate an air of extreme contrition, but somehow I doubt that it gets across.
What do you use?