I tried to create a simple as possible solution to attach LEDs (presoldered strings) into bottlenecks. If you do not use presoldered LED-strings, there might be less complicated ways to mount the LEDs into the bottles.

1. Mark the Dout side of the LED PCB (optional):

2. Feed the LED through the base plate:

3. Place the PCB on the wedge, the Dout side must face to the two little fins:

and bend the wires around the wedge

Insert the wedge into the baseplate:

Now push on the cap and lock the wedge with a bolt (for thermoplastics 3x10). Note the form of the baseplate, it matches to the counterpart in one direction only!

Finally, snap the socket to the sodabottle. Optional fasten the cap wit a 4.8mm cable tie.