sister,

inshallah may you increase each day with strength.
as everyone has already said - you cannot eat or drink whilst fasting. But with regards to after the fast, at the end of the day when you have finished the fast - drink plenty - so that you are not so dehydrated - sometimes this can be the cause for that headache towards the end of the day. Drink ribena or something like that or water to help you replenish what you lost in the day. That is what they meant by drinking plenty. I hope this makes sense.

Porridge.weetabix - usually pretty good stuff. and in the morning before the start of fast drink a glass of milk(unless you had milk in the cereal) and drink a few glasses/a glass of water.

I hope this helps, and is adequate advice you inshallah.