I also have used film canisters for loads of stuff over the years. Post washing of course. I wouldn’t microwave food in them, but I don’t really microwave food anyway. 
I like that the film canisters have really sturdy sealing lids.
If you were looking for more food safe options, I’ve been really happy with small sized Nalgene bottles - they don’t leak, and they come in a variety of tiny shapes and sizes.