1) Click "Edit" on "Scenarios.meta" or "Propsets.meta".
2) For "Propsets.meta", search up "drink_beer" and replace the vanilla prop with the one provided here:         <Item>
          <Name>Prop_CS_Paper_Cup</Name>
          <Variations type="NULL" />
          <Probability value="1.000000" />
        </Item>

3) For "Scenarios.meta", its a bit hard to explain, so I provided a pic on what to do. Simply search up "partying" and follow what the pics show.

4) After that, you should be good.