Rinsing canned sauerkraut reduces its sodium content. Rinse it in the sink with a strainer, mix the sauerkraut with your hands, and thoroughly drain to remove the salt.
Another reason to rinse sauerkraut is to make the flavor milder. The taste of sauerkraut can be a little too sour or briny, and rinsing it off a bit can help make it more palatable.
The main problem with rinsing sauerkraut is that it gets rid of beneficial probiotics, so you may want to avoid rinsing if you are eating sauerkraut for its nutritional value.
However, the majority of canned sauerkraut has been pasteurized. Depending on the brand you buy, your canned kraut probably won't contain any living probiotics anyway.