These lights will definitely add some spunk to any party or kickback. Cheap, small, and bright, they're handy to have around and can make any gathering or drinking game pretty awesome.

Step 1: Gather Materials

Here's all you need for one light:

Electrical tape
Scotch tape
Cardboard (cereal box thickness)
Aluminum foil
1.55V AG13 Alkaline batteries (x2)
LED (x1)
Small zip-lock bag (x1) - usually for small arts and crafts and other such things
Rock (x1) - or other such weight

You can find these on Amazon for cheap or just lying around your house/apartment. If you're planning on making a beer pong set, you'll need 20 lights so just multiply the number of materials by how many you want to make.

Step 2: Assemble

The Light Up Part
- This is where the LED lights up

Stack two batteries, oriented the same way so that the negative end touches the positive of the other
Bend the LED wires as shown to touch the ends of the battery stack. The longer wire of the LED is the positive end and should touch the positive side of the battery stack, and the shorter, negative end should touch the negative side of the stack.

The Tab Switch
- This part acts as a switch for the LED. The foil acts as a conductor and completes the circuit to turn it on, while the cardboard is an insulator and the LED stays off. Tape is used to ensure a smooth surface so the tab can slide between the batteries

Cut a strip of cardboard about 5mm x 20mm
Wrap aluminum foil around a little over half of the strip
Tape the half of strip without foil with the scotch tape
Stick the tab in between the two batteries, with the cardboard part closer to the LED
Push and pull the tab in and out to see the LED turn on and off

The Final Product
- Here everything gets put together and waterproofed to be put into any drink

Cut a strip of electrical tape and wrap around the setup as shown in the picture
Place the setup into a mini zip-lock bag along with a rock (or other weight) to make sure it sinks
Close the zip-lock bag tight