How do I turn off Nintendo Game&Watch?

Solution 1:

As best as I can tell, they cannot be turned off. There is a section about battery life in the Nintendo Wikia page about the fire that says:

With the clock, the battery lasts an estimated 6 months with LR43 batteries and 12 months with SR43 batteries. If the user plays the game only one hour a day, the system would last for six months on LR43 (battery life with SR43 is unknown). The user should notice when the battery's life has been depleted when the screen's display is hard to distinguish.

So it seems you just have to let it run out and replace the battery.

Solution 2:

Out of my own personal experience with a few Nintendo Watch/Game devices, there is no way to turn them off. I tried pressing different buttons, but nothing worked. It is fine though,(You wouldn't turn off a watch, would you?) They do last for a long time. The one I had lasted for more than 6 months, (although I did not use it much).