gas produce gas

it is not hard, every substance can turn to gas in a specify temperature and prassure.
there for you can obtain water vapour by heating the orange juice which is a kind of gas.



Or in the point of view in biology, you can just drink the juice, it contain carbohydrate, mainly fructose. we need enery to stay alive and so we will need tp do respiration(a precess the release energy).
during the process, carbon dioxide is released from our exhaled air and so you can get aa kind of gas.

Since OJ is slightly acidic , you put some baking powder into it , CO2 will be evolved .