I have used the following cleaning agents:
- iRobot hard floor cleaning solution: Pleasant scent, relatively expensive, from a cleaning robot manufacturer (therefore compatible)
- Biohy floor cleaner concentrate for mopping robots: Cheaper

I didn't notice a big difference in terms of cleaning performance.

There is no cleaning agent. But we use Potz Fresh Energy (red) from Migros. 1 capful is enough for the tank. Cleans and smells good 👍🏼

We bought this product and use it with the S8 Pro Ultra:

Biohy floor cleaner concentrate for mopping robots

I don't use any detergent either, just filtered water.
If I see that the dirt is more stubborn (salt and dirt now in winter), I simply let my Roborock run through the room twice. Depending on the view, it first runs horizontally and then vertically. You can set Roborock to mop the entrance area three times in a row, for example. Depending on how hard it has dried, everything is clean after 3 times at the latest.

Hello, yes there are cleaning agents (Roborock Omo floor cleaner) but I would advise against them. The product doesn't mix well with the water, leaves shreds -> combines with the water which clog the pipes over time. And the effect of great freshness is really not there. I personally only use distilled water to prevent limescale deposits.