This version is very easy to build and requires few tools. For building these with real spray paint cans, check out this tutorial:
Step 1: Gather Parts
LED in color of choice
Any type of Wire (22 Gauge stranded works well, 2 colors preferred)
Battery holder for 2 AAA or AA
Momentary Pushbutton Switch (Normally Open, or N.O. on package)
Masking tape (not shown)
Wirecutters (could get by with only scissors in a pinch)
Soldering iron & Solder (optional, can use tape, but recommended)
Drill and/or hand reamer
Hot glue gun & glue
Step 2: Add the Switch to the Cap
Step 3: Wire the Switch
Step 4: Add the LED to the Cap
On the other LED lead, connect your positive wire (in my case this was red). This should be long enough to come out the bottom of the bottle.
Use hot glue to hold the LED in place.
Step 5: Attach the Battery Pack
Tape will hold the battery pack steady inside the bottle.