At some point when I was around 7 or 8, I stopped fully opening soft drink cans. It started as a way for me to 'preserve' my cans as I used to drink a ton of them and so one day was told by my mother that I was only allowed a few per day, but I still do it now. Basically I pull the tab just enough for there to be an opening where the liquid could escape (You'd know when because the gas would escape). The idea is that the drink would foam in my mouth giving me the illusion that I was consuming more than I actually was.

From there there are a few options for consumption. In all cases, because the opening created is indented from back to front, more liquid could escape by holding the can backwards, putting your top lip against the proper opening, and bottom lip underneath the tab. When I was a kid my main choice for drinking was to shake the can while it was in my mouth so that the pressure of the gas would force the liquid out of the can. the second option is simply holding the can reversed and just sucking on it. The third (and stupidest) is for when I am too lazy to even sit up to take a sip while I'm laying down, so I just hold the can upside down so it slowly drips into my mouth. I just swallow every 5-10 seconds.

Usually when I get to the bottom I crack it fully and drink whatever was left, but sometimes I leave them uncracked to mess with people who don't know that I have that habit.