http://www.mcdonalds.com.sg/contactus.html
Btw, drinks left on the counters are not used... but over
prepared... that is still acceptable as it had not been served out
of the counter. Once the food/drinks leave the counter, it had to
be thrown even if the wrapper/cover are all intact when they are
returned.
That is not an issue... I always make special orders... so that
they will prepare new one in front of my eyes.... 
I saw thru the opening to the kitchen how they prepared a
special order or re-assemble "new" order.....
.....I ordered a sausage muffin with egg, they take an existing
sausage muffin left on the shelf for some time and just add in 1
egg patty and re-wrap. Ta da!!! Sausage muffin with egg but only
the egg patty is fresh and piping hot. The buns & meat patty is
stale.
I got to salute to those mcdonalds aunties for really knowing
how to do short-cut jobs and instead of re-doing a new order for
us!!!