It's hard to think of a situation where you would want to say this sentence but I think it's OK grammatically. If you add "too much" I think it sounds more natural, ie "Why aren't you tired?" "Because I've drunk too much coffee tonight".
I typed 'dronk' instead of 'drunk' and it tells me 'you used the wrong word'. There is no such word as 'dronk' in English so i think it should say 'you have a typo in your answer'. That is usually what happens.
The standards seem to be 'I have drunk' and 'I drank' in the main varieties of English. A quick search of the web for 'I have drunk' or 'I have drank' or 'drunk vs drank', etc finds several explanations.