There's some stuff that could work pretty quickly. If it is a more brittle sword, you could probably manage to snap it by driving it into the ground and applying leverage. Swinging it hard into something hard (eg rock or tree) could achieve the same. If it's a softer blade you'd get a decent bend in it instead. If it's well tempered, you're going to have a hard time doing this.

You could ruin the heat treatment if you got a fire hot enough (although this seems like a lot of work), and then bend or break it at that point.

Throw them in a convenient nearby large body of water (this is probably the easiest and most effective).

Grab a whetstone or some other abrasive rock and blunt the blade with it. Alternatively hitting something hard would usually cause some chipping or rolling on the edge resulting in a much blunter blade.

Depending on handle construction, you could also remove the handle and then dispose of it (eg by burning). The problem here is that an opponent could conceivably use it against you still (same goes for blunting it).