Materials: 1w star led, 2 transparent plastic cups (should be identical sizes), toggle switch, AA battery holder for 3V. Thin straws were meant to be used for wire holder, but got excluded during the process because they rather made the structure more complicated than making it simple.
First, I heated up the needle (the one I used was bookbinding needle :/) with lighter, than made two holes for wires. One hole is for plus and the other is for ground.
The next step was placement of toggle switch. I marked the approximate location of the switch and made holes with heated needle as I did for wires. The battery holder was attached with glue gun, but the switch and led were attached with super glue.
Soldering time! Ground (directly from the battery container) and plus wires got soldered to the led. Then both of the plus wires attached to the led and the battery container got soldered to the toggle switch.
Last step was cutting out some space from the second cup for toggle switch and overlaying it. By putting the second layer, the led is now protected and the flashlight can stand upside - pretending to be a normal cup.
To make it more dynamic, there can be different colors or textures applied to the second cup!