Angelus All Purpose Foam Cleaner

What materials can I use this foam cleaner on?

It is suitable for smooth leather, oiled leather, suede, nubuck, and horsehide, though you should always test an inconspicuous spot first.

Do I need to mix it with water?

No water is required; you simply spray the foam directly onto the surface, let it work for a few minutes, and wipe it away with a towel or brush.