Stay put while eating
Unlike here in the US, eating while moving about is not okay in Japan. People will consider you a rude, sloppy person if you eat or drink something while walking somewhere. If you purchased something at a 7-11, sit down and enjoy the view while you snack. Remember, people. Patience.
However, there are exceptions to this rule. For instance, if you have an ice cream cone, feel free to walk about and munch on your heavenly snack. For some odd reason, this is not rude or sloppy, even though you might get it all over your work clothes. Also, you can hang around a vending machine and drink while standing up.