When you wake up after a good party in Cannes you can have a wonderful walk in the old part of the city. You can see adorable old houses and narrow streets. Walking down to the coast you can call at one of the little restaurants and have a delicious lunch. You can also have famous "crepes" (my favourite is with chocolate and cream) at one of the cafés.
Then you walk through Rue Meynadier where you can buy all the stuff for the beach and a lot of tasty things. There is a wonderful shop with fresh seafood.
In Rue d'Antibes you will find good shopping and tasty macaroons in Jean Luc Pele shop!