sup m8 is used as a part of the internet lingo and means "suprise mate!". It's a common word used in games or chats, when you dont have time to write. sup m8 is often used similar to hi.
Jack: sup m8, got sum noice memes 4 u
Dan: Hi bro, send em 2 my discord profile, im in game right now.
A male/female who is one's buddy, companion, or lover over the internet in chat
Great b8 m8, I r8 8/8
M8, stop hogging the ball
If m8 stands at the end of the sentence and does not make much sense, in this case, m8 is pronounceв as might (which is by the way is another way to say mate). This word should mean maybe, but in fact it just does not mean anything
im gonna play computer m8
the weather is good m8
Basically mate, just written in acronyms.
Person 1: Hey m8, wassup?
Person 2: nm (nothing much)