Nah, it's just a way to make himself look better and the nanny worse. He essentially reimbursed her for miscellaneous expenses that come with raising kids (his example is if one of the kids wanted fast food after soccer practice or something) as well as groceries and the like. It's not really a "nanny expense" and more of a "child expense" where the nanny just so happened to be the one to make the purchase. There's no reason to even bring it up other than so that he can technically say "I paid my nanny $90k a year to get drunk on the job and abuse my children."
Edit: there may have been some amount of "tipping" so to say. I.e., when the nanny took one of the kids out to McDonald's, she got herself a small fry. Rekieta may have just included the price of her fries in the reimbursement because why not. When I was in high school and had my license, my mom would ask me to drive to Target to pick up a few things, and she would sometimes cover the price if I wanted a soda or ice cream or something small.