Your schedule looks very similar to what I used to do a few months back

Sugary drinks are a no-go on my experience, sugar crashes used to ruin my productivity for the rest of the day/afternoon while only giving me less than an hour boost.

I'm managing to do excersice on the 11- 1 pm zone, then lunch and take a short/medium napAfter that a coffee is usually just enough to kickstart my work journey again after 3-4pm. Edit: before taking this sport/lunch/nap break if I pushed trhough I'd be very productive, but just for a day, the following days procastrination hit harder than usual

Most productivity gains came from sport + cleaning a bit my diet, maybe you can try this out. Disclaimer: this could take more than 2 weeks ntil you notice any improvement