My 4 year old female pug sometimes breathes water in when she takes a drink and then has trouble breathing. She hunches over and hacks and snorts and seems in distress. What can I do to help her when this happens and how can I prevent this from happening again,

Unfortunately it's a common problem with flat faced breeds.
Even my dogs will chortle and cough if they drink to fast and mine have long noses.
If you watch a dog drink they actually flick the water up into their mouth with their tongue, and sometimes they can flick up t their nose if they are trying to drink too fast.
However sometimes it can actually be a problem with the dogs throat and they have trouble swallowing, it's best to get him checked out by a vet to rule out this problem.