I don't think we ever had 3 liter Pepsi or Coke in Calif. We have Shasta 3 liters at times.
I don't know about other parts of the country, but out here, other than off brands, you just don't see 6 packs of major brands. You either get 2 liter bottles, 12 packs or 24 packs. 6 packs are a thing of the past.
Does anyone out there remember when you would buy bottles of Coke and Pepsi in 6 oz bottles? 7-Up was a 7 oz. bottle that actually had pieces of lemon and lime floating in the bottle. At the Jersey shore at the concession stands you had to leave a 2c deposit and it was returned to you when you brought back the bottle. My cousin and I used to walk around the beach and under the boardwalk looking for empty bottles to return to the stand to collect the money for the return and then go into the 'Penny Arcade" to play the pinball machines. Some of these stands would make us go back to the ocean to wash out the bottles from sand before they would take them.