I always found Guarana to be a long lasting, strong, caffeine type buzz. It has other xanthines and I think it somehow locks them up (in fats or something) so they time release.
Anyway, even as a person who loves their coffee, it was a next level caffeine buzz. Bordering on speed like, but a caffeine buzz.
I'm talking getting actual powdered Guarana and mixing it with cold water and drinking it fast. It doesn't dissolve.
Anywho, I'd imagine it would be like withdrawing from a strong caffeine addiction. Caffeine withdrawals aren't horrible, but they're not mild, for me.