I don't have sandles for cycling in, but I do have a pair of 'Crocs'. They are ultra lightweight, very comfortable, very airy, and can be used for going anywhere (except mountain climbing.) I initially only wore them for showering in or river swimming (not wanting to possibly cut the soles of my feet - not knowing what was under the water on the river banks.) But I got lazy and started wearing them for cycling in too. Though, I only wear them for cycling when there are long stretches of open seldom used roads.
Consider 'Crocs', I recommend them.