@Slola26 ,
If a company wants to sponsor you , they have to draft a letter on their letterhead stating specifically the amount and the reasons of sponsoring your education. What benefits will they derive from such a huge investment ? Especially if it is a profit making company. If it's not a donor company or research funding company , you need to provide the company's Bank statement, certificate of registration, tax clearance certificate, invoice or receipts. However , if it is a prestigious company in your country and recognized with good sponsorship history, they just have to write a letter (letterhead) stating the amount they are willing to sponsor, the reasons and benefits of their sponsorship.
Hope this helps. You can pop me for further clarifications if deem necessary.
All the best
Cheers!