Mondays and then make something from scratch on Wednesday so Dad can have leftovers for the weekend. My go-to "just heating something up" dishes (and Dad's) are Gorton's fish (either battered or baked), Mrs. T's pierogis, Great Value Southwestern chicken pasta (surprisingly delicious!), Amy's cheese enchiladas, Marie Callendar's chicken pot pies, Stouffer's meatloaf and Oncor's chicken parmesan (obviously not as good as homemade, or restaurant, chicken parm but honestly not bad). And, unfortunately, Dinty Moore beef stew once every few months. I don't hate it but I'd be fine if we never had it again.
Unfortunately, I have to cook from scratch more than I'd like to because probably 90% of the prepackaged meals are too high in sodium for Dad.