I’d be real careful about buying alcohol from a pharmacy. I believe they add something to it to make it undrinkable or else everyone would buy cheap alcohol from the pharmacy to beat the tax man.
Pure grain alcohol from a pharmacy is not the cheap stuff. What makes you claim that? It’s fully taxed at the going rate. You might be confusing this with rubbing alcohol sold at US drug stores perhaps? Hey, it’s a pharmacy FGS, they’re not about to poison you if you tell them that you want pure grain alcohol.
But go ahead and con your friends into carrying a highly flammable substance - probably illegally - on an international flight. They might send you a Thank You note from prison...