Traveling in Spain from San Sebastián to Bordeaux, France can be challenging since there are no direct trains between these two cities; so here is how it is done. First you need to catch the Euskotren from the Amara train station (not the RENFE from the San Sebastián station) and take the train to Hendaye ( Spanish/ Basque spell it Hendaia). The ticket machine will say Irun, ugh! So BUY the ticket for Irun which costs around 3 euros and takes about 40 minutes. The ticket agent may say Irun and Hendaye are the same. Actually Irun is on the Spanish side of the border with Hendaye (French spelling) being on the French side. When you walk out to the train with your Irun ticket the train will say Hendaia. Part of the confusion arises from the Spanish and French rail lines. They have an agreement that Spanish trains can go as far as Hendaye in France while French trains can go as far as Irun in Spain.
Next, after arriving at the Hendaye station in France you can continue on via the TGV train to Bordeaux. The travel time takes about 21/2 hours at a cost of 30 euros. Easy!