How can I wake up refreshed after a really late night?

Unfortunately in those nights where you have very little sleep the body is unable to incorporate the proper sleeping cycles and as a result you will not wake up refreshed.

You could try taking a ginseng supplement first thing (do not take at night as it will keep you awake!) as this may help with energy levels however there are certain contra-indications with this and you would have to check if it is OK for you to take first.