Mr.sanjok, you can apply for Hk visit visa for your friend at the Immigration Department of HKSAR government, you should provide the following documents as a sponsor:
Application for Entry for Visit/Transit (Sponsor) in Hong Kong (ID 1003B)

Photocopy of the sponsor's Hong Kong identity card

Photocopy of the sponsor's travel document containing personal particulars, date of issue, date of expiry, and the latest arrival stamp/extension of stay label in the HKSAR (for non-permanent resident of the HKSAR only)

Your friend should send you the following documents if you apply for visa for him:
Application for Entry for Visit/Transit in Hong Kong (ID 1003A)

The applicant's recent photograph (affixed on page 1 of the application form ID 1003A)

Photocopy of the applicant's travel document containing personal particulars, date of issue, date of expiry and/or details of any re-entry visa held (if applicable)

Photocopy of proof of the applicant's financial standing, e.g. bank statements, savings accounts passbooks, tax receipts, etc. and proof of employment (if any), e.g. company leave letter, salary slips, etc.

Photocopy of proof of transportation arrangement, e.g. flight itinerary

Photocopy of proof of the proposed leisure visit to Hong Kong, e.g. receipt of joining a package tour to Hong Kong, itinerary, etc. (for leisure visit only)

It will takes 4 weeks.