Buy Nothing Day has been a holiday tradition for well over a decade. It is the Friday after Thanksgiving in the USA and the Saturday afterward in Europe and the rest of the world. It is described as a general strike against the consumer culture that tells us that we have to purchase something to make us happy and that if we reduce our consumption that the world will collapse.
Over 24,000 people on the Buy Nothing Day facebook page say they plan to participate. In San Antonio it will likely be an event celebrated individually but you might find some solidarity by attending the San Antonio Environment Meetup Green Cleaning Meetup where attendees will be mixing less toxic versions of household cleaners.