"Ga i ddiod?"
Translation:May I have a drink?
Wouldn't it be 'Ga i 'n cael diod?' to translate as the 'correct answer' (May I have a drink) given for 'Ga i ddiod? ' Or is this slang?
That's not quite correct, you don't use 'yn' with Ga i. The correct way of saying your suggestion is 'Ga i gael diod? I've heard this sentence many times in Welsh medium secondary schools but although not incorrect in terms of grammar it is actually repeating the verb 'cael', since 'Ga i' is a form of the verb 'cael'
'Ga i gael diod' means 'May I have receive a drink' or 'May I receive receive a drink'
So there is not need for the extra 'cael' and the correct phrase is 'Ga i ddiod'.