Really how can you tell? Katherine Harmon article explains
long-standing debate among the caffeine-wary is whether decaf served in restaurants is actually what it's billed to be – or is really a cup of the high-octane stuff. Among the skeptics? Read on.
Do-it-yourself caffeine detectors called D+caf Test Strips will tell you if your beverage is – or isn't – the real thing. Just stick one of the tiny strips into a spoonful of coffee or tea (sans any milk or sugar, which eliminates drinks like lattes and sodas) and you'll have your answer in less than a minute, according to Discover Testing, which makes the strips. If the line above "D" (decaf) on the strip is darker, you're good to go; if it's darker above the "C" (caffeine), beware – your drink probably contains more caf than you'd like.
