Replying to Consequences of getting caught doing something illegal in a foreign country?

My school is taking a trip to spain and I signed up. I'm not sure if I want to smoke or drink over there because I don't know what would happen if we got caught. I haven't looked up the drinking age in spain but I doubt it's low. So anyways what would happen not only over there but when I got back home if I got caught either smoking weed or drinking??

P.s. I decided to post this in NSG because I didn't think it fit either 420 or ladies men so I am praying that I still get some good answers instead of a troll fest.