Distillation, but if you are talking about wine/beer:

https://www.nature.com/scitable/topicpage/yeast-fermentation...

"Most yeast strains can tolerate an alcohol concentration of 10–15% before being killed. This is why the percentage of alcohol in wines and beers is typically in this concentration range."

I assume temperature and other factors play a role in how successful you are at keeping them alive that long though.

Distill

Brewers reused yeast skimmed from the top of fermenting beer ("barm"). Wikipedia's "History of beer" article quotes a 1557 source mentioning this, and it probably goes back much earlier. The motivation here is probably speed and reliability of fermentation, which are obvious benefits to people not aware that yeast is a microorganism, but it also incidentally breeds for alcohol tolerance (especially considering the popularity of strong beers). Reusing wooden brewing equipment without sanitizing between batches has similar effects.