So, is that "fake" funny? Is there any difference beetween "hehe", "haha", "huh", "heh", "hahaha", "ha", and so on and so forth?
(AmE) (I assume you mean sounds actually pronounced, rather than sound of genuine laughter, or written.)
Title question: Yes.
Sarcastic? Yes (if said in response to someone else's remark)
Fake funny? Yes, or "just kidding" (if said after one's own remark)
"hehe" - not common, but same as haha
"haha" - see above
" huh" - usually "huh?" means I didn't hear you, or didn't hear you clearly. . what did you SAY?
"heh" - not common, I would take it llike "eh?" as in what did you mean?
"hahaha" - like haha , only more sarcastic, especially if slow
"ha" (usually "hah!") - not even funny, just I don't believe it.
"huh", "heh" are more indicators of surprise. Such as when as when you realise that some money has been deducted from your bank statement: you may make a sound "huh"?
And "ha" is when you catch someone out. "Ha, so it's you who took my pen!!"
But all the others are just laughter. Nothing fake about them, and no sarcasm at all.