Is it okay to drink acid?

Yes , if we talk about some acids Infact we drink some acid like citric acid in lemonades, vinegar is also use in cooking. But only weak acids can be used for edible purpose due to there sour taste.

E.g

carbonic acid- in cold drinks

citric acid - in lemonade

acetic acid (vinegar)-in pickles.

but strong acid may be life threatning in concentrated form.