There are several possibilities. 1) Could be a health issue: check with your vet to make sure he's not diabetic or having kidney problems and if he's getting processed pet treats these may be heavily dosed with sugar. Mine get plain cereal (eg Kix, rolled oats, puffed rice or unsweetened Cheerios), grrens, carrots, strawberries, orange, cherry tomatoes and some fruits . 2) The bottle may be leaking: filling it to the top may help this. 3) The pig may be bored: he needs safe, nontoxic things to chew; He should have a salt lick available. Alfalfa cubes, hay stackers and similar chews will give him something to do.