Bottle cleaning can be a tedious and time consuming task to perform. As such I have been trying to experiment with creating something to clean bottles, similar to projects using the FastRack bottle drying tray (e.g. https://www.youtube.com/watch?v=_iJcG6HbSsE).
The prototype consists out of 20mm outer diameter PVC conduit pipe with 5mm outer diameter copper pipe glued in 80mm intervals 3.5" intervals (estimated to be the distance of FastRack, without actually having a FastRack to measure from). The copper pipe is slightly squeezed together at the ends in order to increase pressure within the system.
The centrifugal submersible pump used can be bought off Aliexpress and is roughly sufficient for 4 bottles at a time (but cheap enough if more are needed): https://www.aliexpress.com/item/New-10L-min-12V-DC-Mini-Brushless-Motor-Submersible-Water-Pump-3-3M-Amphibious/32731443626.html
The bottle holder is a quick 3D printed mockup (took roughly 7 hours to print, so not really suitable for the entire device but good for testing):
Update: I ended up ordering a Fastrack, and the 3x4 bottle tray seems to have a hole distance of 80mm (surprisingly metric ☺).