The British rider hit the Spanish tarmac but dusted himself off and returned to the track unharmed to set a timed lap in the region of 1:41.
Team-mate Loris Baz was not far off the pace set by Sykes, but Kawasaki's team policy of not using transponders meant neither rider's times appeared on the official circuit timesheets.
Meanwhile, Sylvain Guintoli appeared on an Aprilia RSV4 Factory machine for the first time, suggesting the Frenchman remains in pole position to secure a ride with the Italian team for next year, even though there is no official word yet.
Guintoli was among the best of the rest, along with Eugene Laverty and Michel Fabrizio.
Leon Haslam's effort of 1:42.039 was marginally quicker than that of new team-mate Jonathan Rea, who was testing 2013 parts on the PATA Honda CBR1000RR.
Jerez World Superbike official test times day two:
1 Sylvain Guintoli Aprilia 1'41.283
2 Eugene Laverty Aprilia 1'41.762
3 Leon Haslam Honda 1'42.039
4 Jonathan Rea Honda 1'42.108
5 Michel Fabrizio Aprilia 1'42.114
6 Alex Hofmann Aprilia 1'43.028