I've been on methadone for 18 months. Sweating is my #1 side effect. I've found that eating/drinking something super cold helps a lot when I start to sweat. My treat of choice is 1/2 of a freezer pop (you could have a whole one, but I try to stay away from too much sugar). I eat it slowly to try to cool off. You can also pack a glass with ice and have cold ice water. The water is probably better for you, but the freezer pops are a lot more fun!