I work in a business (sales) where I interact closely with the clients....in the past week I've had

[Demonaut]

three separate instances where my clients have mentioned their adult children have died, 2 suicides and a tylenol od.

this is out 7-8 client interactions...and my job is not related to this sort of information.

I feel honored that they feel they can share with me but I never know what to say but the standard "I'm so sorry for your loss"

Any recommendations on something more appropriate?

[dixiegrrrrl]

1. Tone is more important than words..

and less is more.
A simple statement, said with sincereity, is all that is needed.
You can say how sorry you are, there will be a pause, and then you can ask "would you rather meet at another time"?
which gives them the signal to switch gears.
that pertains to your business relationships, of course.
For someone you know on closer terms, you could add " I cannot think of anything more devastating"
(esp. in cases of children, adult or not, dying).
that usually brings forth a gush of words and feelings, so be prepared to respond with "I am so sorry" again when there is a pause.