<v-autocomplete
    v-model='route.city'
    label='Город'
    :items='route.cities'
    item-text='name'
    item-value='uuid'
    @input.native='loadCities'
    @change.native='loadCities'
    return-object
    cache-items
    hide-no-data
  ></v-autocomplete>

this.item.city = 2;

this.item.city = '2';