How many days do I need to wait to drink alcohol after sclerotherapy?

There is no relationship between drinking alcoholic beverages after sclerotherapy. Perhaps the confusion is that people get dehydrated if they drink too much alcohol and dehydration can lead to sluggish blood flow and cause clot formation but this is not supported by the literature. 

I know of no bad effects related to drinking alcohol after a sclerotherapy treatment regardless of the solution used for the sclerotherapy.  Certainly 3 days after the treatment is sufficient time for the solution to be out of your system.