Colonoscopy prep

I’m having a colonoscopy and wondering what will be ok to eat. I’ve read about clear soup but wondering if that’s something I could buy easily from the shop and should I remove any food from them e.g noodles etc. if I just try a black coffee, am I allowed 1 sugar in it? I don’t want to do anything that will affect the tests. I generally only have one or two meals a day, so I just need ideas for a little something to put me on. It’s the lack of coffee that will be the challenge lol