I mainly drink water, alongside protein shakes and coke zero sometimes. Otherwise its probably just drinks/shots when hanging out with friends depending on what we're doing.
Water, since I don't have to waste my time and money buying other drink. I just boil the water then put them into the fridge, since the cold prevent the metallic taste.
For me, it's tied between black tea and flavoured sparkling water. Used to drink about three or four Pepsis a day in my 20s, super glad I replaced that bad habit with these healthier ones.