Are cards like Yuppie Water, that don't say "Potion" on them but LOOK like Potions, considered potions for rules purposes?

If it's a liquid in a container, it can be considered a potion. (But note that other types of one-shot Items, such as Grenades and Ichors, must include that specific word! Potions are special. Also note that Ichors aren't Potions and Potions aren't Ichors.)