I've never used a bidet, do they use a water/soap combination or just water?
I think most are designed for use with just plain water. I saw this one that has a reservoir for some sort of soap or other liquid product with an option to use that before rinsing.
https://biobidet.com/pages/bio-bidet-bb-3000-premium-bidet-cleansing-features-video
There's nothing particularly dirty or salacious about this, but I'm not going to include any quotes. However, this one has a reservoir for the use of different kinds of soaps or other personal care products. Apparently it works by turning it on and pressing a dispenser button to release into the stream.