I have a urea breath test and I can't eat or drink anything 6 hours before the test not even water. I've drank water because I get dehydrated easily?

Urea Breath Test. In order for the test to be correct you have to follow the directions exactly. No one is going to get dehydrated in 6 hours if you stay inside in air conditioning and don't do anything. You don't drink that long when you are asleep. Get the test scheduled for early morning right when you get up.
Water before test. If it was a small amount such as a few sips it would not ruin the test results.