How to clean water buildup on shower doors?

Here are a few suggestions:

cut a grapefruit in half, sprinkle kosher salt on it and use as a sponge to scrub

Lysol 10x power in the blue trigger spray bottle and scrub

Wet & forget shower for a no scrub cleaner that will work over time (not safe for marble)

Whatever you use to get the doors clean, I highly recommend using wet & forget shower weekly to keep it clean.

CLR is a great product to start with. Especially if it’s bad.

You can check this out. https://www.hometalk.com/diy/clean/bathroom/how-to-clean-soap-scum-off-shower-doors-643307

How to Clean Soap Scum Off Shower Doors

Easy does it

Scrubbing Bubbles brand works great if you aren't trying to get away from chemicals. I can't use scented products. I can handle the citrus scent fairly well.

Clean them with vinegar, baking soda, and salt. Stubborn mineral buildup on glass shower doors is no competition for a few common household ingredients—white vinegar, baking soda, and salt. Spray vinegar on the door and let it sit for a few minutes.

I’ve used equal parts warm vinegar to dish soap in a spray bottle, let it sit then a bit of scrubbing. Works pretty well.

After you’ve used the above-noted treatments and there’s still build up around the track and the gaskets,

then take a single edge razor blade, held at a very flat angle and “shovel”, like a snow shovel, the remaining residue.

Make that removed residue is thoroughly flushed down the drain or it will re-deposit itself.

I heard vinegar and baking soda works well