This is a myth that has been overblown by the media. It might have even started as a hoax, or it may have started with some dealer crushing up the pills to use as a cutting agent for other drugs or some gullible kids hearing that these pills could get you high, using them, and the story spread and was exaggerated from there. There is no evidence that smoking antiretroviral drugs alone causes any sort of high, it makes no sense that it would, and experts say it's highly unlikely. It's possible that some of these kinds of drugs can potentiate certain other drugs, as they can affect liver enzymes, so some people might potentially mix them with specific drugs for that reason, but it's a terrible idea and there are far safer potentiators out there.
Various news reports have made different claims, like one said they mix the drugs with rat poison and laundry detergent, while others say that they mix it with cannabis, while others say it's mixed with heroin and crystal meth. But laboratory analyses of samples of the drug referred to as "Woonga", reported by the media as being HIV antivirals, revealed that it did not actually contain any antiretroviral drugs and was usually heroin (source: CBC Radio).
In conclusion, don't believe everything you hear and do not smoke antiretroviral drugs.
Please PM me if you have any questions.