alt Hacker NewsPersonal experience. Then I found many well known programmers shared the same experience online. It feels deliberate work without sugar. ie. if coding = work + fun. without sugar its just coding = work. It does not get any better after 3 days or so too.
It might feel good but spiking your blood sugar isn't healthy for you, and the crashes afterwards will get worse over the years. Improving metabolic health might be a better long term solution; have you explored how endurance or high intensity exercise affects your focus?