OP is lucky that they didn't get hurt, too. "Acid" often isn't LSD--it's often other psychedelic drugs like NBOMe's, that have a narrow window between a physiologically safe dose and a dose that can cause cardiac arrest, internal bleeding, gangrene of the limbs, and other nasty things. It's naive to buy acid and trust the dealer that it's LSD and that the dose is 100mcg--even if the dealer truly believes it! They probably bought it from another dealer, after all.

Hmm. I don't know if anyone catches COVID from COVID-infected people's unfinished beverages being in the fridge, but if you can't do that and don't want to throw it out, hmm. If it's the acidity that hurt your throat, maybe try neutralizing it by adding some baking soda? This will make the lemonade salty, so not do this if you're restricting your sodium intake. If you do, add the baking soda carefully to avoid it fizzing out of control and making a mess.