What do you mean by not healthy? I know at Christmas, most foodbanks try to add some extra treats like biscuits, cake or chocolate, to cheer things up for families that can't afford to buy these things themselves. So if they are well-stocked with the healthy basics, that may be why the list is requesting 'unhealthy' food.
Our local foodbank is short of some basic supplies, but are also asking people to consider donating Christmassy stuff and last month were asking for choc advent calendars to give to the children. I always give advent calendars to the foodbanks as my godchildren get about 6 each so don't really need more from me!