In my first few weeks and months without a drink, I was so tired.
I also got that slump at 2pmish.
I think for me, the tiredness was a result of years of not sleeping well. Most nights I went to bed really drunk and passed out as opposed to falling asleep.
I found that having a sugary drink or a sweet snack - like a cake, ice cream or doughnut - helped revive my energy levels.
What I would say is now is the time to listen to your body.
If your body needs sleep, give it sleep.
Eat well.
Keep hydrated.
Some exercise early evening might also help.
I wish you the best xx