make a waterfall bong. Just put a hole at the bottom of a bottle and let the water drain out when you spark the bowl were the cap is. I use a socket for the bowl. If you wanna take it on the go, you might be able to put some tape over the hole, and put another unmodded bottle cap on top. Since its a bong hit, there wont be much smoke. Although, i dont know if it would work to wait for a while to hit it.

You could always roll a joint and smoke it in public. Were is it that you dont wanna smoke?