I moved to Wisconsin about a year ago. Given time constraint, so far I found no suitable container to carry water or coffee around with me outside. I found that a flask is classy and convenient. But I am not sure if drinking something out of a flask would get me into some trouble, especially a legal one?
If by flask, you mean a hip flask- an iconic representation of a character who drinks alcohol to excess/at inappropriate times:
Then sure, drinking from one in public is fairly obviously going to put a target on your back, just as carrying a pair of bolt cutters and wearing a balaclava might. "I get head colds officer, and I work in a factory cutting chains to length" might be the truth, but it's not a good look for a peaceful life
There are other vessels you can drink from in public that will arouse much less attention:
- a vacuum flask - good for keeping anything hot or cold that way, typically used for hot drinks
- a sports bottle - typically more often seen held by a young or casually/sports clothing dressed person. If you're a flat-cap-and-glasses type who shaves irregularly you might be better off with something else
- a sigg bottle - a non insulating screw cap bottle, often branded. Probably the closest thing to a hip flask in terms of functionality and physical properties, without being the shape that leads to assumptions
- a branded reusable coffee cup with lid - like what Starbucks gives you but not disposable
- a travel mug - an insulated cup usually with handle and some sort of sealable lid, narrow base for fitting into a car cup holder and a widening neck for additional liquid volume
- a disposable plastic water bottle - no one says you can't reuse them, and they sometimes come with a convenient pop up/down sports cap but they tend to shrink if you pour boiling water into them..
"If it looks right, it is right" - not many cops are going to sit down next to you on a park bench and ask what you're drinking on a cold winter's day if it's a steaming brown liquid coming out of a steel vac flask. Unless it smells like it's 50% brandy, of course :)
Regardless of what the law says, you may frequently get questioned by law enforcement officers who see you drinking from a flask. Every time you will have to explain and probably prove that it is not alcohol. It would be like drinking water from a vodka bottle; even though you aren't breaking any laws, you will draw the attention of both cops and civilians (who may report you to the cops).