Hey Minky,
Don't worry, its easy. If you have ever tasted 'milk of magnesia' then thats what it tasted like when i had it.
Quite simple, drink the fluid and then ( in my case) they x-ray my stomach four or five times over about half an hour then back to bed. Now i was an in-patient at the time.
You will be fine don 't worry.
Chin up
Bruscar