A "needle freak" is a user of illicit intravenous drugs.
A "hot shot" is a lethal injection of heroin or other opiate given to the user on purpose. It can be lethal due to extreme purity leading to overdose, or due to being laced with a poison like strychnine (the former is much more common). Dealers will give them to customers they suspect of working as police informers. Addicts will give them to fellow addicts in order to rob them of drugs and/or money, or as revenge for perceived injustice or insult.
"Baked turkey" is not drug slang, but possibly an attempt at a humorous metaphor for a deceased drug addict.
("Cold turkey" is the sudden stopping of taking a drug to which one is addicted.)