Which documents will my Indian sister need from me to apply for a German Schengen visa?

First of all, I don't know any more about this than you (at least prior to this research) and the following is just the result of using Google. In general, don't rely fully on advice given by strangers on the Internet. Check sources, and ask embassies/consulates for clarification when in doubt.

According to this long checklist, one of the things Indian nationals need to submit when applying for German Schengen visas is:

Proof of accommodation for your entire stay in the Schengen area.

Your sister will stay in your place. This means you will have to submit a copy of your (the host's) ID and Passport as well as proof that you can support her stay. ^Source

For this reason (and other ones as well) send her copies/originals of:

• Your Indian passport.
• Your German residence permit/visa.
• Sponsorship letter (if your sister can't prove that she can support her stay financially.)

^{(Potentially relevant document.)}

• Invitation letter (If your sister can and will prove that she can support her stay financially.) Please note that this and the sponsorship letter may have to be a special form that you can collect at the Aliens Authority (in German: Ausländerbehörde). Your signatures may also have to be approved by a licensed notary.

^{(Potentially relevant document.)}

Please note:

Please do not send any invitation letters to the Consulate General, but to the applicant him-/herself. Please also be informed that the original of the invitation has to be given. Faxed or e-mailed invitations from individuals and /or companies inviting Indian nationals to visit Germany and /or Schengen Area will not be accepted.

• Your housing contract.
• Receipts or a bank statement showing that you have paid rent in your place of residence.
• Proof of ownership if you own your own house/appartment.
• Employment contract and salary slips to show that you are financially stable.

I'm not saying all of the above will certainly be needed, but they may all be useful. (And some of them are certainly required.)

There may be more. Keep checking here for more answers/updates. And again, do not rely overly on advice given here. Confirm with official sources.