<span>ipsum</span>
<span>dolor</span>
<span>sit</span>
<span>amet</span>
<span>consectetur</span>
<span>adipisicing</span>
<span>elit.</span>
<span>Voluptate</span>
<span>provident</span>
<span>error</span>
<span>odio</span>
<span>aliquid</span>
<span>quam</span>
<span>excepturi</span>
<span>consequatur</span>
<span>tenetur</span>
<span>enim</span>
<span>iusto</span>
<span>impedit at</span>
<span>illum</span>
<span>tempore</span>
<span>ducimus,</span>
<span>inventore</span>
<span>veritatis</span>
<span>fugit</span>
<span>quod</span>
<span>expedita</span>
<span>iure!</span>
<span>ipsum</span>
<span>dolor</span>
<span>sit</span>
<span>amet</span>
<span>consectetur</span>
<span>adipisicing</span>
<span>elit.</span>
<span>Voluptate</span>
<span>provident</span>
<span>error</span>
<span>odio</span>
<span>aliquid</span>
<span>quam</span>
<span>excepturi</span>
<span>consequatur</span>
<span>tenetur</span>
<span>enim</span>
<span>iusto</span>
<span>impedit at</span>
<span>illum</span>
<span>tempore</span>
<span>ducimus,</span>
<span>inventore</span>
<span>veritatis</span>
<span>fugit</span>
<span>quod</span>
<span>expedita</span>
<span>iure!</span>

body {
  display: flex;
  flex-wrap: wrap;
}

body::after {
  content: '';
  flex-grow: 9999; /* =) */
}

span {
  flex-grow: 1;
  text-align: center;
  background-color: #ccc;
  padding: 5px;
  margin: 5px;
  border-radius: 5px;
}