I have watched for a long time how to flush the toilet of EMU trains. There is no button and it is not automatic. Similar to this one in the picture, I haven't found such a punch after looking for it for a long time. If it is a toilet, it will flush automatically after the lid is closed.

If you are squatting, look around to see if there is a logo in the picture, press the button or touch the button (maybe an inductive switch). Or you can stand on the other side of the squatting toilet, and the machine may think that no one will flush automatically when squatting.

Extended data:

Motor train and full-name power vehicle refer to vehicles equipped with power devices in rail transit system, including locomotives and power cars. Motor vehicles are equipped with driving wheels, and the corresponding vehicles without driving devices are trailers. If the train can run normally on the track, there must be a moving car to provide enough traction for the whole train, but it is not necessary to hang a trailer without power.

EMU is a railway vehicle equipped with wheel-driven mechanical equipment, not an EMU. Not only high-speed trains have bullet trains, but all types of vehicles, including constant-speed EMUs, ordinary-speed trains, subway trains, light rail trains, monorails and maglev trains, have bullet trains.

References:

Baidu Encyclopedia-Emu