All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
A group of contemporary scholars hold the view that the encouraging prizes given by banks to investment account holders are permissible as long as the prizes are from the bank's money and not from the depositors' money.
In our view, in order to be on the safe side, it is more appropriate to refrain from taking such prizes to avoid the difference of opinion, because some scholars stated that it is not permissible for either party of Al-Mudhaarabah (i.e. the holder of the money and the one who works with the money) to gift each other, unless the gift is given for a reason other than Al-Mudhaarabah.
It is even with greater reason that one has to refrain from taking such prizes if the motive for the person to open an account and deposit money in it is to enter the draw in order to win prizes. In this case, he would be like the one who gambles with the money which he had deposited in the bank.
For more benefit on Al-Mudhaarabah/Al-Muraabahah, please refer to Fataawa 306337, 276166 and 244552.
Allah Knows best.