At my former company we had free access to beverages (sodas, water, energy drinks, ... even beer). I gained a lot of weight while working there. After I quit I stopped drinking sodas altogether, while mainly keeping my diet (vegetarian, one "big" meal per day + snacking) and level of physical activity. I lost about 18kg (40 pounds) in about 2 months. Went from 103kg to 85kg. I'm 1.84m so that's an ok weight I guess.

So that worked for me ... drinking water.