Energy drinks are notorious for being sugar packed, aside from containing ridiculous amounts of caffeine. The only thing I can think of, aside from coffee and tea, is vitamins. Vitamins C, B and D seem to provide an energy boost. The downside is that if your body doesn’t need any of them, it will just flush them as excess.
I loved the Hi Ball Energy Seltzers I felt like they were perfect for fasting.
I fast from 4pm-10am. Wake up at 5am and drink a Celsius Energy drink on my way to do my morning 5k followed by weight training. I also where a CGM and I know that for me, Celsius doesn’t cause a blood sugar spike. I have done this for over a year with zero issues.