I don't have a food bank locally, but the Lion's club does a collection annually. What I try and do for it is (over the weeks in advance, a few things a week), buy what a family of 4 (ish), including a baby and child, might need for a week.
Pasta and a couple of jars of sauce
Rice and a couple of jars/packets of sauces
Tinned tuna, tinned sweetcorn
Porridge oats (breakfast and loads of other uses)
Flour
Dried fruit (snacking and baking)
Washing powder, washup liquid
pack j cloths
Household cleaners
Nappies
Kids meals/pouches
Biscuits
cereal
squash and fizzy drinks, longlife OJ and apple juice
toothbrushes
Showergel, shampoo, conditioner, toothpaste
bin liners
toilet rolls
kitchen rolls
tea, coffee, hot chocolate, sugar
ketchup and mayonnaise and mustard
mixed herbs
I can't even remember it all, but generally a full trolley-load of the kind of everyday things that are useful, as well as some seasonal treats to enjoy.