If you into it you will find tea is popular with monks for sustaining meditation. Tea has more than caffeine, there are other useful compounds as well. Much better for focus than coffee.

If you are good at power naps (i.e. can drift off in under 10 minutes in the right conditions) you can try a tea rebound nap; make a strong cup of tea and drink it quickly just before you lay down for a snooze. You'll drift off before it hits and by the time your 20-25 minute timer finishes your brain is doubly refreshed.

I find the 'hard-reset' aspect of a nap to be essential some days, and it is completely different in nature than the 'energy' aspect. More to do with unresolved problems to solve than actual energy.