It is NOT incorrect but it isn't what you're trying to say. "I've had some tea already." = I've had some tea recently, just now. It would often be a polite way of refusing another cup (because you've already had a cup!) Mr. X: "Would you like a cup of tea?" Mr. Y: "No thanks, I've had some tea already. Thanks anyway though!" --- "I've had some tea before" has a different meaning. It means that at some earlier point (in your ENTIRE life) you have had a cup of tea. Therefore it doesn't fit in the context above very well. You could use it to say you've tried tea! Mr X: "Hey, have you ever tried tea? It's so nice! I especially love green tea!" Mr. Y: "I've had some tea before. I like English Breakfast tea personally." = I've had tea at some point in my life and I like English Breakfast tea in particular. When you use "some" you suggest that you've only had it a few times/not a large amount. You can remove the word if you drink tea often! You could use the construction in other ways: Mr. X: "Have you ever tried snails?" Mr. Y: "Oh yes, I've tried snails before. I had them when I was in France back in 2008." -- Hope this helps. Good luck :)!

"No thanks, I’ve had some tea before." "...before what?" is my question. The sentence is incomplete.