If your budget allows you

to consider buying gift cards now for those Saturdays in the future. I know right now many restaurants are running specials that if you purchase a gift card of a certain amount you get a smaller gift card for free. If you are a member of mypoints get your gift cards through them and get bonus points for doing so. Sign up for emails from your favorite restaurants and you will get a wealth of coupons—I have a separate email address for just such things. I also get the free restaurant loyalty cards that net you free food.
Also as others have mentioned cigarette lighter devices. I have a small “ice” chest that is either hot or cold that plugs into a cigarette lighter (aka: hot spot) that I have kept many a meal warm in. Also you can use “solar” to heat things up. I’ve heated up many an item in the past in foodsaver bags on the dash of a vehicle. Park the car so the sun shines in on the pre-cooked food packet through the windshield all day and you will find you have a hot meal waiting for you.
My mil had an electric coffee carafe that never saw coffee. When dfil was a traveling salesman she would pack it full of soups, stews, chili etc and he’d plug it into his cigarette lighter as he traveled. Visit any major truck stop and you will see a wealth of cigarette lighter gadgets. WORD OF WARNING these do draw on your vehicle battery when the car is not running, so be aware of this. If you have a weak battery you might not want to use such items without periodically visiting your car and running the motor for awhile. If your drive home is long then you could “heat” the foods with these devices as you drive home and the meal would be hot when you got there.