Hi,
Not sure if this will help at all.... but my son gets out of his routine every now and again and I end up getting up at all hours of the night to calm him down so my husband can sleep.
What i do now is i sneak in after he has gone to sleep and put a sippy cup of water in a corner of his crib. I also put a sippy cup int he same corner at nap times so he can see where the cup is. it takes a little while of me getting up to give him the cup and then he realises it is there and finds it himself during the night (make sure it is a very well sealed cup as you don't want to be changing all the bedding during the night)
I also tell him that his waking up at all hours is making mommy sick and then i can't play with him during the day. So if he sleeps all through the night and gets up when it is morning then we can have more fun because mommy and daddy are happy and not soo tired.
He is almost 27 months old and i have been having this discussion with him on and off since he was 18 months old. Usualy his sleeping gets messed up when he is teething or has a cold or some such thing. i have learnt not to let him repeat the waking up for more than 3 nights otherwise it seems to be harder to get him back to sleeping through the night.
Also, I slowly weaned him from a full milk bottle to a water only sippy cup over a number of weeks so that his tummy could adjust to not having food during the sleeping time.
Hope I haven't rambled on too long.
C.