I might object to someone taking a break before a 3rd set TB since the match is almost over. After sets, I could care less if someone wants to take a 5-10 minute break. If I run out of water, I'll usually just ask a teammate to fill up my bottle. However, if there are not any teammates around (which never happens) I would think it reasonable to get some water. I would just be really quick about it. In my years playing USTA, the rules are not followed very closely. Nobody is timing breaks.
Please excuse my punctuation and grammar.