If they are in under 5 gallons each, I would just load 'em up and put them on the seat next to you in the car while you're driving or, if you can, have someone secure them by just holding them between their legs, etc. If they're in anay more than that, I would empty out half the water ( to make them lighter and easier to transport ) and do as stated above. It's pretty straightforward. Bettas are very hardy fish and since you are not moving that far, it shouldn't really be that much of an issue.