depending what quantity you have,you may find someone running an older diesel engine could use it. i used to put a small amount of petrol in the diesel of my lorry years ago to stop it waxing up.
obviously you can't do this with modern cars but big lumpy lorry engines won't mind a small amount mixed in with a full tank of diesel. possibly a tractor/farmer.
failing that ; molotov cocktail for mad ken in london. (i'm only half joking! )
Best bet is to get rid of it in the used oil at your local tip. This is recycled for various uses. Better this than to use it in an un-safe manner. I wouldn't use it for paint brushes as the petrol can cause skin disease and the diesel element would leave a residue on the brushes.