Hibiscus Tea should not keep you awake since Hibiscus Tea does not contain any Caffeine.
And because Hibiscus Tea is an herbal tisane that means it doesn't contain any stimulate including Caffeine like other teas to keep you awake.
Hibiscus Tea is good for lowering blood pressure and for detoxing your body as well and since it doesn't keep you awake at night it can help you relax at night and could also help you fall asleep.
I know Hibiscus Tea helps me to fall asleep and it's very good for you as well.