I take my last amoxicillin treatment (14 days) of 1g twice a day ( h.pyroli infection) this morning. can i have an alcoholic beverage tonight?

Not good idea: Anytime you are on medication, alcoholic beverages shouldn't be taken at the same time. With your history of h. pylori, you need to be cleared of it thru a breath test, (or stool sample or both). Having ethanol on board is just not a good idea. Ask your doctor when you can have or resume alcohol. In general, it affects your GI tract, and immune, and neurological system & not wise to do.