You might consider serving Onion Straws.
Onion Straws are like very thin stringy crisp onion ring-strips and are fine for packing with a dog into it's box ... or as a separate side.
Take onions, slice them fairly thin on a (deli) slicer and then manually separate each ring - retain only rings that are approx 2" across or larger for straws ... and then, pull each ring apart as well, so it becomes a strip (manually with your fingers ... not with a knife)
Put the onions in a ventilated tub (lexan etc) and let sit in the walk-in for 2 full days to weep.
On the third day they are ready to use.
Make a well combined egg wash with eggs and milk.
When you have some to sell - or are backing up some to sell very soon ...
Put a handfull (etc) of the onions in the eggwash, then allow to drain for a minute (a chinois works good for letting them drain) then, dump them into a fry basket that is in a tub of (regular) flour; cover with flour and shake basket to sift the flour thru the onions - coating completely. Transfer them from the flour basket to a fry basket that is being used in the fryer ...
Immediately lower into the deep fryer and keep some cooks tongs at hand to turn the straws in the basket as they cook and to keep them separated. They cook in about 3 minutes so you have to watch them closely. Drain briefly, transfer to a hotel pan under the heat lamps and dash with a little salt.
Alternately you can fry the straws in a smaller fry basket - not separating them, and using a second basket as a weight on top, to produce an onion 'brick'.
These would make an awesome addition to dogs.