I was able to get hold of an anchor cup for the first time in a while. It's a glass container that was made to replace canned food around the time of World War II when there was a shortage of metal, but since the top is not sharp, it can be used as a cup.
The capacity is about 150ml, about 80-90% full. It comes in three colors: clear, aqua blue, and aqua green, but the stock of each is limited.
Anchor Cup