Nothing to do with bento but it is still Japanese. I’m sure if you’re a fan of Japanese culture you’ve heard of Ramune, a soft drink with a very unusual bottle. The bottle’s lid is not a screw top like British drinks but it is a marble held in the neck of the bottle stoping the drink from leaking out. To open you use a little “pusher” to pop the marble into the bottle with a satisfying *POP*.
I found this in my local Chinese market and while not Ramune it is, as far as I can tell, the same type of bottle but branded as EDO (it may be Ramune just rebranded for overseas markets). This was peach flavour and was 95p. It was amazing and the flavour was a lot stronger than I expected without being overpowering. The lemonade flavour is delicious too!