We went to the park with DP and DD this afternoon. We were sitting by the sandpit. There was a woman sitting nearby with an about 8 month old playing with sand. All of the sudden she come to us and asked us if we had water as she had to make up the bottle for her dc. We looked as sometimes we have small bottles of water lurking in the basket under the stroller but we only found on, half-full bottle. So we said sorry, we haven't got any and she asked for this bottle
. So I said that I'm not sure when it was opened and who drunk from it (i.e. me, DD or DP) and she still wanted it! So I said that I'm not sure it's a good idea to give it to the baby and she said "really, do you think so?" and seemed totally unconvinced 
So am AIBU for thinking it's very strange to want to give your baby bottle of old water from which a stranger have drunk?