瓶 and 缶: containers and quantities
Distinguish bottles from cans and read empty containers, remaining contents, and counting units.
A bottle as a container
瓶, read びん, means bottle. 瓶に水を入れました。 means putting water into a bottle, not putting the bottle into water.
空の瓶を洗いました。 says that someone washed an empty bottle. 空の rules out adding contents such as water or another drink.
A can as a container
缶, read かん, means can or tin. 缶のふたを開けました。 means opening the lid of a can.
缶にお茶が少し残っています。 says that a little tea remains in the can. Do not turn a small remaining amount into a completely empty container.
Container counts and volume
ジュースを瓶で二本買いました。 means buying two bottles of juice. 二本 counts bottles, not a volume of two liters.
缶を三つ並べました。 says that someone lined up three cans. It does not specify what they contain.
Does 瓶で二本 necessarily mean two liters?
Show the answer and why
No. It means two bottles. Each bottle's capacity requires separate information.