Economical water heater

Economical water heater for shower water:

If you had barbecue on the campside and no warm water here is an opinion:
You need:
-1m Silicone hose D10mm
-2m copper pipe D10mm
-the printing part for the decathlon shower or
-the printing part for the Hühnersdorff canister
-a camping grill or another fireplace

Twist the copper pipe around a bottle, so you get a coil like in the picture. Connect the silicone hose by putting it on the copper pipe and on the printed nozzle (or stick it in th