This depends on your age.
If you are below the age of 16, you can get the Children’s daypass (‘Kindertageskarte’ / ‘Carte journalière enfant’) for just 19.- a day. Otherwise, most offers do not differ between youth and regular customers. The only thing - if useful - might be the GAnight, which is avaliable for people below the age of 25 and valid starting 7.00 p.m. each day untill 5.00 a.m. the following day (except 7.00 a.m. on Sundays).
If you are above 16 years old, keep in mind that you need to buy a full-fare ticket unless you posses the Swiss Half Fare Card or the Halbtax.
Which offer exactly do you mean by ‘youth pass’? If you mean the Children’s Co-travelcard, this is only valid when accompanied by the person with whom the Co-travelcard is issued. It is not transferable either for the child nor for the accompanying person.