Help! Book on trash/items thrown away in HK? (Hong Kong)

Hello Hong Kongers!

I'm finishing an illustrated book on trash/trashcans and need to know what 2 typical items one might find in a street trash can in Hong Kong and Macau. There are photos in my book I took in HK (Chi Lin Nunnery) and Macau (historic quarter). Any ideas? Something typical (i.e. not just plastic bottles etc). In Macau, I thought perhaps something to do with betting? Chips or betting cards?

Macau has no internations forum, hence my using this one.

Many thanks for your ideas! Any other info or articles etc re waste local collection issues is welcome too, it's very precious to have local knowledge on top of the web. I'm happy to credit contributors in my book if you can help.

Best wishes & thanks from Paris,

Phoebe