Is it possible to fake being drunk?

My friends are encouraging me to drink, so what I intend to do is order diet coke in a spirit gl and pretend to be weary and fall asleep. They won't know what I am buying and it is the same colour as rum and bourboun and cola. I don't want to be pressured and want to fit in. Would you be able to tell if I was really drunk or not? If I say I don't drink, they call me boring and a square and say I am old fashioned and no fun.