Unless otherwise recommended by the manufacturer, only water. I only use decalcified water for my robotic mop. Otherwise there is a risk that the water pump in the devices could be damaged.
As an alternative to Eufy, however, I would recommend the Xiaomi Dreame D9. It offers excellent laser navigation, always knows where it is, is very robustly built and cleans the flat systematically. It also has a very large dust bin, so you can let it run longer before emptying the dust bin. It also has a mopping function, also with an electronic pump.
Xiaomi Dreame D9