What kind of liquor is in schnapps and can you buy it straight?

Jade Orchid asked:


I have a customer (I work at a liquor store) that wants to buy a liquor that tastes the same as what you would get in schnapps but he wants it unflavored so he can “experiment” with different flavors. He wants something with very little after taste that’s not too high in alcohol content. Thanks!

Mercedes