I'm from Sri Lanka, and have jumped through many bank statement hurdles (the lawful way).
Most of the bank accounts here are savings accounts, and the money is readily available to withdraw (I.e accessible funds - not fixed deposits or anything). They come with a passbook to record transactions.
However, for visa requirements, customers can request the bank to provide a statement of transactions or a balance confirmation.
If your friend plans to pay for the visit and stay, make sure he has sufficient funds for that. A statement (3 months history) is usually OK, but some countries (Japan for example) require 6 months back.
Banks also provide bank guarantees based on fixed deposits + land property + vehicle + other assets. These are a bit difficult to get (statements only takes a few minutes), and are usually viable only to guarantee assets worth more than 1 million Sri Lankan rupees.
I think the best way would be that you provide the embassy a letter that you will be sponsoring for your friend (unless he can prove he has more than a reasonable amount maintained in his bank account for 6 months), which is up to your bank to provide.