Yes, the Friends Day Pass for Youth is also available for foreigners. The only condition, everyone has to be under 25 years (24.99 years of age).
Friends Day Pass for Youth. | SBB
However, if you plan to visit the Jungfraujoch, the Swiss Half Fare Card is strongly recommended. The high ticket costs for a full fare ticket legitimates its purchase. And, my advice, do not buy Jungfraujoch tickets in advance. It would mean a waste of money if the weather is not favourable.