Sympathy Heave (I'd want it to be Sympathy Puker, but I don't think that terminology is quite appropriate)
General
Feat 1
Reaction
Trigger: You have the sickened condition and a creature you can see within 30ft succeeds on a fortitude save retching to reduce the value of their sickened condition.
The sight and sound of vomiting has always caused you to sick up as well. Immediately attempt a Fortitude save against the DC of the effect that made you sickened. On a success, you reduce your sickened value by 1 (or by 2 on a critical success).
I don't think this feat is exactly good but I think it's funny, has a reasonable use case, and it's pretty believable.