I'd say that if serving unasked water to 20 customers in a restaurant makes one of them order one glass less of beer, wine or soft drinks, then the environment

I'd say that if serving unasked water to 20 customers in a restaurant makes one of them order one glass less of beer, wine or soft drinks, then the environment has won. The amount that people actually drink (or pour away from table) is completely negligible when compared to the amount that is used for production of industrial goods (including beverages). (Of course the restaurants then loose money if people don't buy beverages, so it's not in their incentives to serve water, which is probably why such policies exist in the first place: it's green-washing of greedy actions.)