Eating good balanced meals every day is what you need to do from here on. Yes you also need to be drinking plenty of water every day as well.Not sugar drinks which most fruit juice and fizzy drinks are full of.DO NOT drink milk to try and flush your system out as others have mentioned,they are not right here.Also ...Vegetables are far better than fruit but you need fruit as well to balance things out.
In the morning try drinking a large glass of hot water,nothing in it at all, just water.As this will help you body get rid off unwanted toxins and start the day of clean.I have a friend who many years ago use to hike for days and with out much fibre and good foods in his system ,because you simply couldn't carry what you need with you,but the only way he would flush out his body was to drink hot water to stop being constipated. Not having the right amount of fibre in the body as a regular thing isn't something long term you should be doing but the water helps.Also perhaps for right now,go get some prune juice or better still eat about 6 or so of them.