Suggestions needed on diet

I recently started a very physically demanding job (roofing). I'm 5'11, 175 lbs. I'm looking for suggestions on what kind of diet I can maintain to help me adapt to 12-14 hour days of hard labor and have it actually be good (or at least not detrimental) for my overall health. I have time in the late evenings where I could meal prep for the next day. I don't even really know where to begin with this. My diet right now is around 3 to 4000 calories a day, mostly pizza, McDonald's, spaghetti, cookies, cake, and soda -- this diet maintained me at around 185 lbs when I was working behind a desk, but closer to around 3000 calories at the upper estimate for daily intake. I drink about a gallon and a half of water each day, and feel slightly dehydrated toward the end of the work day. Muscle pain lasts multiple days between roofs; deep aches, not like tears or anything, but if there's a dietary change that would help me recover more quickly, that'd be awesome to know about.

Thanks ahead of time for any information or suggestions you guys can provide.

Diet will be supplemented with stretches recommended by my doctor and a yoga instructor.

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