NO NO NO
dude, honestly if you want to smoke just small amounts at a time i would highly recommend investing in a one-hitter that costs just a few dollars
you can probably find one at your local gas station
do not make shitty homemade devices out of soda cans, pens, and other shit as in the long run it will screw up your lungs unnecessarily
if you NEED something for right now make a pipe from an apple, best route IMO
edit: actually read your post...if you can't afford a one hitter how are you getting your weed man? just scrape together some change and get the pipe, my opinion stands