Is it possible for breakfast before a blood test to distort ggt result?

Yes: A GGT test needs three days on a diet with about 150 gm cabohydrates each day, and an overnight fast (at least 8 hours) before the test.

Which test?: If you mean "glucose tolerance test", then breakfast beforehand will ruin it, as will not complying with the preparation. If you mean "gamma-glutamyl transpeptidase / transferase" or "drunk screen", breakfast matters less, but be advised that some normal non-drinking folks have a hereditary tendency to run a very high GGT and I have to write letters for a few such folks each year.