You can legally enter Spain on a Schengen visa issued by another country such as Switzerland, as Ajax rightly pointed out.
However, in order to persuade the Swiss to issue that visa you need a convincing plan. Hotel reservations are all very well, but you are likely to get asked questions such as "What are you planning to do while you are in Switzerland?" - so what you should do is sit down and plan a trip to Switzerland as if you were really going there.
The other option would be to fly to Spain via another country, preferably with a stop-over of a day or more, and get your visa from that other country. I can't remember the precise wording, but I understand that you are supposed to get your visa either from your main destination, or from your first point of entry if you are visiting several countries. If you are planning on spending one day in Switzerland and five days in Spain then technically you should still be applying to the Spanish embassy as your main destination, but I can't somehow see the Swiss embassy turning you down, especially if you explain that the Spanish embassy didn't have any appointments available.