I'm not sure that anaerobic strength should be the goal. But, I would think that would be maximal short-term effort, say for 1 or perhaps 2 minutes.
A number of people recommend intervals.
They could be done on the flat, or on a hill that would take a couple of minutes to get to the top. Just hit the hill repeatedly.
You can play around with the effort based on speed and gearing. For better or worse, there is nothing that beats a hill that knocks you just over the top of the gearing you have on your bike. For example, do your hill climbing with a 13-17 straight block freewheel.