Hardware arpeggiator, software or Sonar's MIDI track built in arp?
So long as the drums are in time with Sonar's metronome any software arp run as a plugin or a component in a software synth should be in time automatically.
For hardware you need to make sure the hardware is connected so it receives MIDI clock and stop/start from Sonar (as well as cabling you need to emable clock send in Sonar's project preferences).
That should sync everything. If you want the arp to respond directly to the MIDI in the drum track, say only operate when a certain drum is hit, things get much more complicated. For that you might be better recording the arp as MIDI, editing that MIDI manually so it does what you want then using that as the source for the synth playing the arps.