I wouldn't use the energy drink bottle for a gas tank... just not safe...
Try looking on ebay or other places for a small used welding oxygen tank like those ones that are for those portable oxy-acetylene setups, you may be able to find a used medical oxygen tank for even less, and the medical ones are made from aluminum instead of steel... One of those bottles could be had for about $50 or less, then paint it blue and put a NOS decal on it. The Acetylene tank won't work, but the oxygen tank looks just like a Nitrous bottle and holds anywhere from a quart to a few gallons of fuel depending on size. An empty fire extinguisher bottle will also work well, look the part and be safe.
To prepare it for gasoline use, you'll need to drill and tap a hole in the bottom for the fuel valve and remove the regulator on the top to swap it out for a screw on cap. The cap will also need to be vented to prevent fuel starving from the vacuum created in the bottle...
The B size, C size, M6 or M9 type cylinders would be about the right size for oxygen cylinders and you can find them used on ebay for a good price... Far safer than a plastic soda bottle and it'll look way cool once painted and the NOS decal is added, not to mention there's no fire hazard if you tip over or from the bottle leaking etc...
Here's a link for a bottle I found on ebay after a quick search...
http://www.ebay.com/itm/B-Size-Alum...959?pt=LH_DefaultDomain_0&hash=item3a9168b29f
There are a lot of fire extinguisher bottles that have the same shape and size as well, so whichever costs less, but these would be safe to use and will last unlike a soda bottle that could give at any time.