Alcohol wipes then wipe all areas off with a microfiber cloth. My case I wash with soapy water and a old tooth brush. Wipe dry let it sit for 30 mins. Do that once a month. My phones always look new when I trade them in.

There are a lot of suggestions on the net for that. I have tried them all pretty much and none of them last long. The only one worth a damn is make a paste of baking soda and sparkling water. About 2 tablespoons of each. Wash your case really well with dish soap first then with a cheap toothbrush scrub the paste mix on the inside and outside of the case. Put a good layer on it and let it sit 10 minutes. Then rinse it off really well. Dry it completely. It will look better. I gave up on clear cases. None of them stay clear.

Wipe it with alcohol pad first to remove all oils and such first.

Get a automotive cleaner wax. Use a small amount on a microfiber cloth. Do not get any in any ports or holes. I did my neighbors and it looked really nice.

I have AppleCare + on my iPhone 13 Pro Max but I still use a case. I always have. I will only use one type of case OtterBox. The Defender. I have had my phones fall off roofs, been thrown across a room, stepped on, etc. They have always been fine. Except once. Ran over my X with a lawn mower. Apple care sent me a new one. So I recommend both. It’s worth it to protect your money.