Possible Duplicate:
“A/An” preceding a parenthetical statement
is the correct form
A (sweet) apple
because the article "A" precedes the word sweet, although it is put in brackets (as a side remark), or is the correct form
An (sweet) apple
because the effect of "sweet" on the form of the article has been nullified by the brackets?
One might argue this depends on whether I regard the word within the bracket to be pronounced when the text is read aloud.