JSFiddle - React, Tailwind, and code Playground

HTML

<div class="modal fade" id="modal-edit-veiculo" tabindex="-1" role="dialog" aria-labelledby="modal-edit-veiculo-label" aria-hidden="true">
    <div class="modal-dialog" style="width:80% !important;">
        <div class="modal-content">
            <div class="modal-header">
                 <h4 class="modal-title" id="modal-edit-veiculo-label">Novo Veículo</h4>

            </div>
            <!-- modal header -->
            <div class="modal-body">
                <form class="form-horizontal">
                    <div class="col-md-6">
                        <div class="form-group">
                            <label class="col-sm-4 control-label" for="unidade-veiculo">Unidade</label>
                            <div class="col-sm-8">
                                <select class="form-control modal-detalhe-veiculo-unidade-veiculo" name="unidade-veiculo">
                                    <option>Selecione uma Unidade</option>
                                    <option value="001S000000nlKu4IAE">Teste 2</option>
                                    <option value="001S000000nmTBdIAM">Inpulso 04</option>
                                    <option value="001S000000nm2EiIAI">Teste Inpulso 8</option>
                                    <option value="001S000000nm2deIAA">Teste Inpulso 10</option>
                                    <option value="001S000000nm2fGIAQ">Teste Inpulso 14</option>
                                    <option value="001S000000kHf7lIAC">RMR COMERCIO E TRANSPORTE DE GAS LTDA.</option>
                                    <option value="001S000000nJfoyIAC">Santos</option>
                                </select>
                            </div>
                        </div>
                        <div class="form-group">
                            <label class="col-sm-4 control-label" for="placa">Placa</label>
                            <div class="col-sm-8">
                                <input type="text" class="form-control...

JavaScript

j$ = jQuery.noConflict();
j$("#cancelar").on("click", clearModal);

function clearModal() {
    document.querySelector('.form-horizontal').reset();
}