I've just returned from Belgium by coach but that's obviously not as far as you are travelling. I'm presuming your coach does food?
Wear loose fitting clothing as you don't want anything 'digging in'.
Take some wet wipes and tissues. (Tissues come in handy in case coach runs out of loo paper also).
Panty liners are handy too.
A battery hand held fan.
Small deodorant..
Most of these can be bought from the travel counter at most supermarkets in travel sizes.
Ipod, book etc.
Neck pillow/eye mask
Little snacks that aren't too messy. I took some of those tiny packets of individual cheeses, chewy sweets etc for the munchies, couple of boiled eggs & crisps. Individual cartons of drinks or plastic bottles of drinks.
We didn't have food on board so we did ourselves a little packed lunch but the coaches do stop enroute for refreshments.
We were in Tossa last year and I thought it a canny little place