I love the idea of indoor water play and the pudding art sounds great too! I sometimes get the kids to 'help' by washing the smaller toys (like the plastic food we use in the kitchen). They really love it and the older ones have a great sense of accomplishment and take great pride in their work.
I personally don't use sensory bins because my group is very young and smaller objects are a choking hazard. I also don't believe in wasting food (although I know you can create sensory bins with non-food objects). I also feel like what we do every day is sensory - feeling the mud, holding worms, splashing in puddles, picking grass, etc. so don't really see the need.