Well, overhere my friends improvise a similar system, using Camellbak's.
One has the coke, the other the ron.
The only side effect is that later, when we actually pour water into the Camellbak, it tastes lake licour. But at least we know it must be desinfected.
I saw Starbucks promoting their coffee by giving out free samples out of this gadget here in Singapore. cool stuff.... but kinda bizarre.