How do you say something is "very alcoholic"?
Per my understanding, alcoholic has two meanings in English:


(Something) contains or is related to alcohol.
(Someone) is addicted to alcohol or is affected by alcoholism.


For the first meaning, in Chinese we say 含有酒精的 or 酒精含量高的. E.g. 


  Alcoholic drink 含酒精的饮品 or simply 酒精饮品


For the second, we use the word 酗酒(成性) (adj.) or 酗酒者/酒鬼 (noun).


  He is an alcoholic. 他酗酒成性 or 他是个酒鬼。




Regarding the Chinese phrases in your question,

酒精很强，很有酒精 means #1 but don't sound natural without context. 

"酒量很高“ or ”酒量很大” means someone is good at drinking. 酒量 is not the short form of 酒精含量, but one word meaning 'the ability of a person to hold liquor'.