However, don’t feed them milk. It can upset their stomachs, so stick to plain, fresh water. Put it in a shallow dish near the food.
Don’t forget that this will only ever be supplemental: a hedgehog’s natural diet consist of bugs, slugs, snails, beetles, caterpillars and earthworms. They have plenty of food to choose from in your garden and will continue to forage for themselves as well if you put out food for them.
This also means there is no need to worry that they will starve if you go on holiday!