I see what you're saying about the portions, and realized this when I started university.
When I drank water at home, it would be in a glass (may be 160 ml glass?) and that is what I did since I was born. When I moved to university, I realized that I could save some costs (and washing up) if I just drank straight out of the bottle. But this meant that I would usually get more water than I needed and this meant that whatever I ate wash being washed out. After my first year, I realized what I did wrong, and bought some glasses, and drank the water.
During the following year though, I was living with a couple of mates, and they had glasses that were at least double in size. When I started drinking water from these glasses, I also realized that even though it may still be a glass, the water is too much, and need to stick to using the portions I have been using all the time. (These were very similar to
Collins glasses)
As far as sandwiches go though, I never made myself that many sandwiches, and neither did my parents while I was at home, so I really don't have any portions to go by.