What other things has he done?
Drinking your water is a complete non issue. Tap water at room temperature is fine and is arguably healthier as there's less thermal shock when you drink it.
If there's something serious he's done, like being violent to you, then you should record it if you can and then start escalating it via your parents. Then Social Services if your parents can't or won't nip it in the bud - if you are basically the victim of domestic violence.
If it's other petty things like cheating at Monopoly or having a bigger slice of cake than you, then just accept and tolerate his behaviour until you can move away from home. Learning to live with the annoying habits of other people is a part of growing up.
You can't control your brother's behaviour. But you can control your own. Try to behave like a grown up angel. Not like a vengeful devil. Don't sweat the small stuff, but if there's anything big and important that needs action from you (like him hitting you), then go right ahead and do whatever you have to do.
As an adult, people will like and respect you more if you are an (assertive) angel. Instead of someone that makes mountains out of molehills, or that carries on vendettas over small stuff.
Sleep on this. And decide tomorrow morning if one stupid glass of water in the fridge is worth any of your time and attention at all.