In most cases, tea or coffee taken without milk are allowed.The day before the colonoscopy, the patient is either given a laxative preparation (such as bisacodyl, phospho soda, sodium picosulfate, or sodium phosphate and/or magnesium citrate) and large quantities of fluid, or whole bowel irrigation is performed using a solution of polyethylene glycol and electrolytes. The procedure may involve both a pill-form laxative and a bowel irrigation preparation with the polyethylene glycol powder dissolved into any clear liquid, such as a sports drink that contains electrolytes. A typical procedure regimen then would be as follows: in the morning of the day before the procedure, a 238 g bottle of polyethylene glycol powder should be poured into 1.9 litres (64 oz.) of the chosen clear liquid, which then should be mixed and refrigerated. Two bisacodyl 5 mg tablets are taken 3 pm; at 5 pm, the patient starts drinking the mixture (approx. 8 oz. (0.5 litres) each 15-30 min. until finished); at 8 pm, take two bisacodyl 5 mg tablets; continue drinking/hydrating into the evening until bedtime with clear permitted fluids. The procedure may be scheduled early in the day so the patient need not go without food and only limited fluids until later.The goal of the preparation is to clear the colon of solid matter, and the patient may be advised to spend the day at home with ready access to toilet facilities. The patient may also want to have at hand moist towelettes or a bidet for cleaning the anus.
(Personal communication to the Joint Commission on Ambulatory Care, May 1983)

Etymology
The terms colonoscopy or coloscopy are derived from the ancient Greek noun κόλον, same as English colon, and the verb σκοπεῖν, look (in)to, examine. The term colonoscopy is however ill-constructed, as this form supposes that the first part of the compound consists of a possible root κολων- or κολον-, with the connecting vowel -o, instead of the root κόλ- of κόλον. A compound such as κολωνοειδής, like a hill, (with the additional -on-) is derived from the ancient Greek word κολώνη or κολωνός, hill. Similarly, colonoscopy (with the additional -on-) can literally be translated as examination of the hill, instead of the examination of the colon. In English, multiple words exist that are derived from κόλον, such as colectomy, colocentesis, colopathy, and colostomy among many others, that actually lack the incorrect additional -on-. A few compound words such as colonopathy have doublets with -on- inserted. See also
References
Further reading
Gupta S, Lieberman D, Anderson JC, Burke CA, Dominitz JA, Kaltenbach T,  et al. (March 2020). "Recommendations for Follow-Up After Colonoscopy and Polypectomy: A Consensus Update by the US Multi-Society Task Force on Colorectal Cancer". Gastroenterology. 158 (4): 1131–1153.e5. doi:10.1053/j.gastro.2019.10.026. PMC 7672705. PMID 32044092. Gupta S, Lieberman D, Anderson JC, Burke CA, Dominitz JA, Kaltenbach T,  et al. (March 2020). "Recommendations for Follow-Up After Colonoscopy and Polypectomy: A Consensus Update by the US Multi-Society Task Force on Colorectal Cancer". Am J Gastroenterol. 115 (3): 415–434. doi:10.14309/ajg.0000000000000544. PMC 7393611. PMID 32039982. External links

Colonoscopy.