How can you say “I’m exhausted” besides “είμαι εξαντλημένος-η-ο» but rather using colloquial or slang phrases? In English would be something like “worn out”, “drained”, “wasted”, «dead” etc

So, here are the most common phrases that are used in more informal and friendly situations.
1. «είμαι κομμάτια»
2. «είμαι πτώμα»
3. «είμαι χώμα»
4. «είμαι ράκος»
+ (από την κούραση)
You can use them adding or not the phrase in the parentheses.
-Θα έρθεις μαζί μας στο πάρτυ;
-Μπα, δε νομίζω! Βγήκα χθες και είμαι κομμάτια σήμερα!
So, next time you want to express your fatigue in Greek, just choose one of these phrases and take your Greek to the next level!
You will definitely sound more Greek! 🙂