<select ng-model="car" >

    <option value="null" disabled >Choose a Car</option>
    <option value="ford">ford</option>
    <option value="chevy">chevy</option>
    <option value="honda">honda</option>

</select>

<button ng-click="chooseCar('ford')" > ford </button>
<button ng-click="chooseCar('chevy')" > chevy </button>
<button ng-click="chooseCar('honda')" > honda </button>

$scope.car = null;

$scope.chooseCar = function(car){

    $scope.car = car;

}