I don't drink a lot and often forget to do so (I'll also forget to each, which I wish would happen more often .
I don't think it's an Autism thing though, just how your body works. It's preferable to being thirsty all the time because that's often a sign of an underlying medical condition.
Still, always a good idea to stay properly hydrated. Persistent dehydration is just not good for you.
When I do drink, the overwhelming majority of the time it's water.
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Always do right. This will gratify some people and astonish the rest.