Has anybody tried cypress essential oil or apple cider vinegar to cure their thread veins?

No evidence: I don't believe there is any credible evidence that cypress essential oil or apple cider vinegar would yield any significant benefit. Laser treatment for facial veins and sclerotherapy for leg veins are the gold standards, with lots of evidence of success and low risk when properly performed.

I hope not: Neither cypress essentail oil nor apple cider vinegar, whether taken internally or applied to the skin can do a thing for thread veins. If you want to treat your thread veins, the gold standard for treatment is sclerotherapy.