Tried ones made out of a different material, they're ****e. Collapse too easily, prone to leakage, difficult to clean well.
When in the Boy Scouts in the 1960s I had one made of aluminum. It worked tolerably well, collapsed to a lightweight, hockey-puck-sized disc that fit in the pocket.
However, its primary use for hiking in the mountains where (and WHEN) streams were clean enough to drink from. Otherwise - why? do such things exist ....
Mine was made out steel I think. But I just don't really see the point. You can't use them to take liquid with you, it's just for scooping.... for which you can also use your hands, which don't take up extra weight or space.
A much better solution, I think, is to use a dopper bottle, which doubles as a bottle AND a drinking glass, and which doesn't leak or become grotty, unlike those collapsible cups.
