What is worse for you – eating a sufficient amount of ‘unhealthy’ calories, or not eating enough calories in general?

I oftentimes struggle to eat enough calories in ways that are considered "healthy," though I do try to be mindful. I'm not eating candy and stuff like that all the time, but I see eating, say, a local burger & fries as an easy way to help me get enough calories in for the day. I struggle to put on weight, and typically if I cook a meal of my own at home, it isn't enough calories (despite being a filling and rather healthy meal). I also have ADHD which causes me to struggle with the executive function of cooking sufficient meals on a daily basis, and going out to a restaurant and eating a burger & fries 3 days out of the week helps me get calories, but I know those aren't "healthy" calories.

So, what is worse for you – eating enough calories, but "unhealthy" calories (burgers, pizza, etc.), or not eating enough calories? (Perhaps for the trade-off of eating typically low-calorie meals due to 'healthier' ingredients?)

Additionally, if anyone has some tips on how I can get SUPER LAZY, SUPER QUICK **HEALTHY** calories for the day, I'd love some advice. I'm talking like, 3,000+ calories made easy.