I would not be carrying these to the parks, they are not refillable there so at best you would have one single serving and have to carry it all day. Other option if you do carry is to fill it with water and add those single serving kool-aid, lemonade, power aid to the water. Park water from the fountain is pretty icky, heavy well taste, which is why I'm sure so many of us buy bottled water.
I believe it would leak in a bag. I just filled mine, upside down it dribbles but the open close has slides on the outer rim, so if it bumps something in the bag it will fully open. Yuck.
Some people are like Slinkies.
They aren't really good for anything,
but they still bring a smile to my face when I push them down a flight of stairs.
Friends are Gods way of apologizing to us for our families.