Have the group sit in a circle. Fill the thimble or bottle cap with water. Have someone be "it". "It" chooses a category such as brands of cars and in their mind chooses one but doesn't tell anyone yet. Let's say the choice is "Ferrari". Beginning at any point in the circle, "it" stands in front of a player and that player has to say a brand of car. If the players says "Ferrari", "it" tosses the water in their face and they become the next "it". Also, if a player says a brand of car that someone else has already said, they get the water in the face and become the next "it". So it is important for players to pay attention to what has already been said.
Here are some suggestions for categories:
Brands of cars
Types of dogs
Countries in North and South America
Large US cities
Halloween creatures (ghosts, goblins, black cats etc.)
Stephen King novels