i love me a mason jar - for food or beverage - especially on the go and because i'm a cheap-o. or you could say i'm eco-friendly, take your pick, at this point it's just seamantics to me. regardless, i always try to reuse my jars. (you can ask my bf - he's usually less than thrilled about my growing jar inventory...)
however, when it comes to beverages, it can be a bit tricky when drinking on-the-go... and then cappow!!! (think batman action word - it will help you understand my enthusiasm).
i just discovered this genius, reusable top - a screw on lid that turns an ordinary mason jar into an adult sippy cup. (get one for yourself - or your jar-loving pal - for only $7.99, i am.)