"Quetsch" is defined as "a dry white Alsatian brandy distilled from fermented plum juice" at http://www.merriam-webster.com/dictionary/quetsch
"Quetsch" means schnaps in German http://en.bab.la/dictionary/english-german/quetsch
"Quetsch nach" means "squish after"
Apparently the true meaning of this phrase is a mystery to many...
