Erm...we're going to have to say no, that's not safe. (Please don't try!) If the vent is emitting a lot of SO2 or H2S, they would taste BAD. And if you add sulfuric acid (in vog, for example) to sugar, you get a pretty spectacular reaction.

— USGS Volcanoes🌋 (@USGSVolcanoes) May 29, 2018