My mom's maltese does this often after drinking water. She doesn't have any health problems, but I do think she is snorting up water. She also does it every now and again when not drinking. We just call it reverse sneezing.
Is this what she is doing?
http://www.paw-rescue.org/PAW/PETTIP...eSneezing.html
She is positively adorable, by the way!