I've used McCormick Old Bay 16oz tins for a small on the go drinking vessel. The plastic lid can be taken off and on for cleaning and easy refilling. It has the snap lids to help contain the liquids and the plastic is not hot to the touch, unlike the lip burning metal of other cups. I slip it into a neoprene coozey to keep it cool to the touch.

It takes a couple of washing to get the smell and taste out of the tin, but some like a little spice in their coffee so do as you wish.

I've never cooked with one so I can't say if you fall into that same welded seam trap as other rectangular tins.