I would treat these as a reimbursement. You put out your money, they reimbursed you with a gift card.
IF your required purchases exceeded the value of the gift card I would claim the excess as 'unreimbursed business expense'.
If the gift card exceeds what you spent I would still just count it all as a non-taxable reimbursement because on a reasonably regular basis I can purchase restaurant gift cards at a 20-25% discount so would not consider them to have the same value as the cash you put out. (And they cannot be converted into cash)
If we stick to a understanding that reimbursements are NOT taxable and fees and bonuses ARE taxable then we can generally logic out what we should be paying tax on. I am always perfectly content (I won't say 'happy') about paying the taxes I am required to pay, but that certainly does not keep me from arranging my life so that there is as little of that as possible. Where IRS has provided a loophole, it is perfectly legal, ethical and moral to use it even if it was originally created thanks to lobbyists pushing for someone else's special interest!