Here are two ibles in one regarding coffee cups.
Please vote for it
I know they are simple but they are effective
Step 1: Paper coffee cup telephone
2 paper or plastic
1 5ft- 200ft of string your choice
1 hole punch
I know this is a basic principle you punch a hole with a hole punch in bottom of each cup and slide a string through the hole and then tie a knot so the string is connecting the two cups togetherand then you are done this is great for little boys and girls who like to spy and chat ( my little bros love this concept)
Step 2: Coffee cup listening device
Who says that you have to have a super genius mind or a super technology to make a high tech listening device well you can make your own with these simple techniques.
1 plastic or paper coffe cup
1 door with people telling secrets behind it
This concept is also a simple one it is very similar to the put your ear against the ground in a field and you will ear a stampede a mile away except you hear everything people say behind the door once you have a coffee cup put the bottom of the cup next to your ear then put the top part of the coffee cup against the door. And you will hear secrets that people have been hiding from you for years.