No you do not use and so on in formal writing.

Hello Aliona, I agree with Ami and Matthew. The phrase is much too informal for anything professional. Matthew's example (better option) is a very good one. But here is another thought I had - something that I personally watch because I am a professional writer. The phrase "and so on" or the abbreviation "etc" (et cetera - Latin for "an so on") is a bit of a cop out (being lazy, if you are not familiar with that term). It tells me that you might have just not cared enough to give me a full view! However, it can also mislead or misinform your reader. "My friends like volleyball, football, tennis, and so on," might make me think that the only sport your friends like are sports involving balls - in other words, they don't like skiing, archery, or surfing, which may or may not be true. Just another thought and probably much more than you wanted! Terry

Yes I think it is too informal for an essay

You should be fine as long as you don't overuse it, but a better option might be: "My friends like sports such as volleyball, football, and tennis"