I have a small desk, so any accessories that gives me more space is welcome.
For desks that are around 1.5" thick, this accessory works great.  There's a spring-loaded clamp that you pull down to attach the holder.

The challenge is, if you have thicker desks - this will not fit.  I have a glass standing desk and this will not fit on that.

The other thing to watch for us the weight of the cup.  I tested a standard cup and it seemed to hold fine, but if I put just a bit of pressure on the holder , the clamp will not hold -- which could be a potential mess!  So yes it can hold the weight of most beverages, but be careful where you place this cup holder to avoid accidents!

Where it works though, the extra storage from having the cup and the little tray to hold extra items is handy.