While slang is not a common ESL textbook topic, it can be fun to talk about slang with your students. There are now 45 slang worksheets that you can use to help your students sound more like native speakers. Here is a slang worksheet that includes a lot of slang and is cleverly organized. Your students will enjoy the challenging exercises but if you think it is too difficult, consider having them complete the activities in groups. This should make it more manageable for them because they can work together. You can find other worksheets on slang in this section so do not feel like your options are limited.
Slang is not formally taught in most ESL courses but is something that students may enjoy learning. Additionally things like ttyl, lol, and brb would be interesting for students who use SMS or texts as a primary method of communication with friends and family members. While slang is not going to be on their college entrance exams, they will certainly be exposed to it when traveling in an English speaking country or when watching movies or TV shows in English. Remind students that while slang is an important part of the English language, overusing slang, just like overusing idioms, will sound unnatural and it is not appropriate in every situation.