You can certainly apply for a public defender and see if you qualify financially. Any lawyer is better than no lawyer.
A couple of responders have commented on the definition of "open container".
The statute says:
"4-251 D. 2. "Open container" means any bottle, can, jar or other receptacle that contains spirituous liquor and that has been opened, has had its seal broken or the contents of which have been partially removed." (Emphasis mine.)
So there very well could be an empty can defense unless, maybe, there was even a drop of beer left in the can.
Once you get the police report you can see what the officer wrote.
I haven't been able to find case law on the internet regarding the definition of open container.
It would be a good idea if you visited the law library and looked up the Annotated Statutes that have appellate cases listed under each statute. Then you can look up the cases if there are some.