Place chicken breasts in the bottom of the slow cooker.
In a sauce pan heat soy sauce, sugar, garlic, and chopped onion over medium heat until boiling.
Pour sauce over the chicken in the slow cooker.
Cook on high for 3-4 hours or low for 6-8 hours.
Serve over cooked rice.
Notes
We also love to serve this with stir-fried vegetables. I just buy a bag from the frozen foods section and fry it on the stove top when the chicken has about 10 minutes left to cook.You could also dump a bag of frozen stir-fried vegetables into the slow cooker for the last 20 minutes of cook time for the chicken.