What water to drink on holiday in Spain - help please!

We are going on holiday to Spain in about 3 weeks. My 8 month old gets most of his fluid from breastmilk, but i have been trying to get him to take more water during the day, especially as it's been so hot the past few days.

I know babies aren't supposed to have bottled water, but the Spanish tap water is full of minerals, so that will be no good for him either. Just wondering what other people have used in the past, is there any bottled water suitable for babies, or is the tap water ok to drink if boiled?

Thanks! xxx