It could be that you’re swallowing excessive amounts of air while you eat or drink. The stomach can’t tell whether it’s filled with food or air, even if you ate a relatively small amount of food. Things like eating or drinking quickly, and not chewing your food thoroughly, can increase the amount of swallowed air. I feel like that's probably the most common cause, besides just simply eating too much. There are also some medical conditions associated with bloating, if you're really concerned about it. One of them is called "Gastroparesis". More information here: http://funadvice.com/r/brvl6eb8kg6.
Almost anything can make you bloat, including water