To use the negative form of ーたりする in Japanese, I believe you should write verb stem + なかったり。 In other words, it would be 吸わなかったり、飲まなかったりする。 However, I am just wondering how this particular sentence sounds in the negative form. One would generally not be smoking or drinking alcohol in class anyway, so the use of the negative たりする construction does strike me as a bit odd? Perhaps a native Japanese speaker can better address this point. I generally use the negative -tari construction only for "doing X on and off", like "drinking alcohol on and off" (アルコールを飲んだり飲まなかったりする). I am sure there must be other ways to use the negative construction, too, though!