That sounds like the procedure my husband had last week. Is it the laxative drinks that come in a 'what to do' pack from the hospital that you take four hours apart? If it is then you really won't want to move more than 3 metres from a toilet.
My husband refused the weetabix or toast and was told they couldn't let him go home so he gave in and ate half a slice of toast.
Fasting is okay as far as your diabetes goes. Google Jason Fung - he's a kidney specialist in Canada who recommends fasting as the best way to control or reverse diabetes. I don't know about the reversing of it but using his guidelines I have often fasted and it has lowered my BG. More importantly, it hasn't made me ill, just hungry.