Was she drinking or not?

Ok so my sister was drinking something out a water bottle so I sniffed the little bit that was left in it, it smelt a bit like alcohol but I'm not sure because it was warm out so I thought I might've been smelling the plastic bottle, I did somewhat of a test and put the bottle in the freezer and after 30 minutes some of it was frozen and the remainder wasn't, do you think there was some alcohol (probably vodka) in there? Also I took a drink and it didn't taste any different then water (well maybe a little different but nothing too strange).