My kids have activities 4 nights of the week, and I am often tempted to run through a drive through because they overlap dinnertime. My kids and I are happier when I pack dinner instead. You can pack leftovers, or you can prepare a meal in a crockpot or another quick meal that packs easily. Stir-fry, burger-type meals, are popular with my crew, but I have showed up to gymnastics with a casserole dish. Now it is a comfortable habit, and better than a drive thru habit!
I use the generic version of the ziploc divided container, available in most grocery stores, to pack these meals. In the warmer months, we pack a "picnic" so the rest of the family can enjoy a meal outdoors while the child with an activity is busy.