I seem to remember that some or most beer cans (Aluminum containers), are inner coated.
I'd stick with jnanian's suggestion - plastic or glass.
For heating, water bath is preferred, rather then directly heating the vessel.
And if you do this with glass vessels, make sure they are not tightly closed, so that when the liquid expands (due to the increased temperature), the glass shatters and the contents go everywhere. Ask me how I know this.
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