we always pack extra food in our bags. We fly Southwest and thankfully, they still allow two checked bags per person. I pack things like Fiber One bars, pop tarts, granola bars, trail mix, cookies, crackers, fruit that won't squish easily, (usually apples, maybe bananas if they are really green), cereal, and the last time because we didn't have a fridge, I bought shelf stable milk in juice box type boxes, I wrapped them in a towel, then in a gallon size ziploc bag in case the leaked, but they were fine. I put anything that might get crushed or crumbly in a plastic shoe box. Everything goes in to a duffle bag to be checked.
I have Brita filter bottles, so we use those instead of ordering a case of water, and we also buy the refillable mugs when we get there so there are options for something other than water to drink.