Let trucks dump current cargo as trash or just lose it

I found myself in a situation that I assigned trucks to sand mining, but did not have any sand storage. It led to a situation where I cannot build storage (because I cannot unload sand) and I cannot unload sand (because I can't build storage).
I wish there was a button on a truck "dump current cargo" or just "destroy/lose/abandon current cargo".

Or a button to tell the truck to store it in the dock and unassign it?