I dont drink that much soda but i'd go with >bottled>can>fountain

Fountain - Sheer quantity, cheap, and sometimes they've just replaced the syrup bag for the dispenser and its super concentrated.
Can - Great quality, moderately priced, and whats better than ripping into an icecold 24-pack. Also slam-cans are amazing.
Bottle - Lowest quality, expensive, and a waste of a huge plastic bottle.

Fountain > Can > Bottle

if you mean glass bottle then that is the best otherwise fountain

Glass > Bottle > Can > Fountain is my opinion to be honest.

Glass is more pleasing to the eye
but it takes eons to biodegrade.

pop*

Glass Bottle>Fountain>Plastic Bottle>Can

soda >

i prefer cans for my sodapop

Fountain > All Other Pops