Lots of foods have naturally occurring sugars,same with salt, it's added refined sugar that you really want to avoid. Sometimes the ready made savoury baby foods also used concentrated juice to sweeten, which is a bit sneaky as you wouldn't do that at home.
The yogurt probably has a bit of fruit juice added? You don't have to buy baby yogurt - any plain organic no added stuff yogurt is fine.
Not 100% sure on the water but think I have read somewhere that the mineral content in bottled water is a bit high so might be tougher on baby's kidneys.
A French friend of mine uses Evian to make up all her baby's bottles, she says everyone does it in France. But personally, I don't see what's wrong with plain tap water? Unless you're on a plane of course! But you still need to boil it, it's not sterile.
Agree with Robin, naturally occuring sugars are better than added ones, but unfortunatley you can't tell exactly how much is added sugar from the labels. I read on here that anything with over 15g of sugar per 100g would be high sugar, anything with less than 5g of sugar per 100g would be low sugar.
With salt/sodium it's different - whether it's naturally occuring or added it's all the same to your baby's kidneys. But generally speaking, if you don't add salt when you cook then you should be ok. Watch out for bread, cheese, salted butter (most UK butter is salted, but you can buy unsalted butter), these are all high in salt.