If he finds himself thristy a lot of the time, he could suck on crushed ice. It seems to work better than plain
water for quenching thirst. and it takes a lot less to get the job done.
If he drinks alcohol, he needs to quit. If he smokes, again he needs to quit. If he has excess weight, he needs to lose it.
If he is sedentary, he needs to get up and move as much as he possibly can, but never to the point of not being able to catch his breath, or carry on a conversation.