Measuring USB power adapter quality using multimeter
Well, "quality" is a complicated term.

While on a first approximation, one might simply say that "doesn't drop below 4.8V even when drawing ${realistic amount} A current", and that's something that you could measure with a simple constant current sink and a multimeter, things get more complicated the more modern USB power supplies become; phones can communicate their power needs, and a supply that works well for one might not be as great for another.

Then, "quality" is also something that you might be measuring in reliability; since no multimeter in this world can't fast-forward half a year to see whether the supply will break, that's not something you can measure.

A very tangible aspect of supply quality is voltage ripple under different levels of load; this has mainly EM noise effects. However, you'd need an oscilloscope with a couple MHz bandwidth and something to draw controllable current from the USB supply to assess that.

So, while you can certainly assess the main "K.O. criteria" (too little current sourcing capacity), you can't do a more wholistic quality assessment. By the way, a clone is probably not the thing that QA labs would usually employ to assess the quality of a device under test – after all, you need to trust your measurement device more by orders of magnitude to come to a dependable quality assessment.