Plastic bottle with silicone, fold-out trough
Cutaway showing the parts and how they fit.
A version with an ABS bottle
You can see more of the internals in this view
A version with an HDPE bottle and silicone trough. HDPE is amazingly strong when thick and maybe the safest plastic to use for consumable liquids. Silicone is considered to be inert. Just watch out for lubricants and whatever else the factory through into the mix.
Here is a simple trough add-on to the ubiquitous SIGG bottle.
...And what it would look like with the flexible trough flipped out.
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Water Bottle System for Dogs V2
This is another attempt at a hydration bottle for dogs. There was concern that the stainless steel version was too risky cost-wise.