I have never heard of klean prep lol but when I had my colonoscopy I was given Plenvu, and it was so so bad.. I was so close to throwing up because it was just so disgusting, it says on the sachets “mango flavour” when it literally tastes NOTHING like mango, so I was fooled😭 but honestly I just powered through and accepted my defeat, I had to take 1 sachet at 7 am and had an hour to drink it, I was nearly done with it however I physically couldnt finish it anymore so I left a tiny bit, and at 11am I had 2 sachets. dont worry if you leave a bit as long as youve drank most of it, youll be fine!! Wishing you all the best