This is a training toy for dogs.
You can put a treat (~1cm size) in the hole at the top that will be dispensed when the button in pushed.

Parts
Rubber bands to the length of your liking
3x M3-inserts (344 size)
3x M3x10 round head screws
3x 4cm PTFE tube, 4mm diameter (optional)
1x Bottom
1x Insert
1x Deckel
3x Plug (for the bottom)
3x Plug2 (for the top)
(The plugs probably don't matter where you put them, but the one of them is just slightly shorter)

Assembly
If you use the optional PTFE tubes so it slides better:

Insert the PTFE tubes into the slots at the corners of the "inlay" print
Slowly insert the insert into the bottom part. If it doesn't slide free, sand/cut the outside of the tube a bit until it slides with little resistence

Insert the M3 brass inserts as shown with a soldering iron or a matching tool
Assemble the deckel and insert part
Using the top (Plug) and bottom (Plug2) plugs, fix rubber bands between top and bottom
Insert the assembly into the bottom part
Mount with the M3 screws