I read a similar thread on here a few years ago, and a MNer who had had to use foodbanks said that she really appreciated getting some non-essentials alongside the essentials. She said it was horrible not being able to give her kids an occasional treat when she was picking them up from school and every other child seemed to be getting something from their parent at pick up.
I think that, if you are having to use a food bank, the odd treat is arguably more important than at other times, because anything that gives you a little lift will help you cope a bit better - whether that is a nice latte for yourself or a little chocolate bar to give your kids.
We do the big shop online now, but dh will put things in the basket at the Co-op if he remembers, and we donate to the Trussell Trust, but when we were doing the big shop in person, I used to fill a bag for the food bank, and I put in mainly essentials - tinned soups, tinned meat/fish/veg, coffee, tea, UHT milk, cereal, sugar etc, sanpro and toiletries, and some treats - chocolate biscuits, cake bars - individually wrapped where possible - and ling life desserts.