I assume your "business" is based on some reality, so just extrapolate and embellish as needed
Really just chatting while they tick off boxes on the application. I use reselling used merch, guy asked where I find my inventory - I think just more curious than anything. I told him about the local auction house that cleans out estates and one of the good finds I snagged. (Genuine vintage Coach purse in a lot of misc handbags) He though that was cool and we moved on to the next question.
Just have answers for what's on normal business account or card applications and
confidence. If you believe it's a business you can sell it as a business. (Which is why we suggest people go with what they know or have done in the past.) Helps to have little anecdotes at the ready so doesn't hurt to rehearse a little beforehand, if only in your head, which helps with the confidence. I haven't heard of any stories where the banker throws someone out because they suspect it's made up or anything like that. They make commissions on new accounts so they want you to succeed... and keep the account open so they can get paid