Which Eye Drops Are Best for Droopy Eyelid Due to Botox?

Most 'droopy eyes' are actually droopy eyebrows due to injection of the horizontal forehead lines (as stated by Dr. Cohen). If this is the cause the droop should improve by gently lifting up the brows. You can try to improve this type of droop by adding more Botox into the brow depressors (the frown lines) and by avoiding as much being put into the forehead lines.
If the eyelid still appears to be partially closed over the eyeball, then it is true ptosis and the iopidine (aka apraclonidine) drops can help till the Botox wears off.

True drooping of the eyelids known as ptosis is rare after Botox injections. If this occurs, the eyelid itself does not open as much as it normally should and instead covers more of the iris than usual. This can be improved with apraclonidine drops temporarily until the condition improves, usually over the course of several weeks.
Much more commonly, the upper eyelid area appears heavy due to depression of the brow. This most commonly occurs from injections in the forehead area without balancing the treatment by performing injections to the glabella and crow's feet in a patient with a predisposition to heavy brows and upper eyelids. When this occurs, Botox injections to the glabella and/or crow's feet can be helpful in some patients. In others, it may simply be a matter of time to allow the injections to begin to wear off.
Always see an expert physician injector.
All the best,

Iopidine eye drops can be helpful for botox induced weakness of the upper lids.  In additi,on botox placed in the lateral bony orbital rim may be of benefit to raise the lateral eyebrow and help the eyelid opening