Spilling leftovers of drinks on plants on Shabbos

Sometimes we drink alcoholic beverages in the park on Shabbat, and often there is some liquid left in a bottle. We want to pour it out before we go, so that the youth who come there won't drink these beverages. The question is, is it permissible to pour it on the grass or do we need to make an effort to pour it down the drain or on a road, etc.?

Dear ...
It is permissible to pour wine on plants since it certainly interferes with their growth; however, other alcoholic beverages such as beer, whiskey, vodka, etc. that contain water are forbidden to pour on plants.

Shulchan Oruch, section Orach Chaim, ch. 336, §3