Business visa (On arrival)
Vietnam business visa is normally valid for 3 – 6 months, and in some cases, you are entering Vietnam for just a few days for business purposes, you can also apply for a tourist visa instead as this makes no difference.
Do you need a sponsor?
Fortunately, no, with visa on arrival, sponsor is not required to apply for a 3 or 6 month visa. However, if you apply for a visa through Vietnamese embassy, they will ask you for a proof of sponsoring letter from Vietnam institutions.
Applying for a business visa is completely the same with a tourist visa, please see details here.
Is it possible to apply for a business visa for tourism purposes?
Yes, you can apply for a 3-6 month visas for both tourism and business purposes.