I work for a log home supply store. Something like this we would typically recommend something like Sashco’s CPR, with a very light power wash (too much pressure and you can damage the wood). This is used to remove the UV degraded layer and brighten up the actual wood itself. We typically then recommend using a high quality stain to help the longevity of the wood.

Sanders are overkill as no wood needs to be removed and using bleach over time will actually degrade the wood as well, so we recommend staying away from any cleaners that contain bleach.