I don't know the current draw but would guess at 100mA @3v. And at a very rough guess also this could be something like 100x the current draw of the garden light.
I'm Guessing as well,
These particular Li-Ion spots are extremely bright, 100 Lumens,
they may have either 1/2 or 1 watt LEDs.
I'm assuming they also have 2 18650 (3.6V) batteries, typically 1800mAh.
So that would be a total capacity of 12.96 Watt hours.
That fits pretty well with the 6 & 10 hour run times they have (switch selectable),
and assuming they not designed to be fully discharging completely charged cells each night.
Had a quick look at some LED specs & I tended to see ratings around 400 Lumens for about 1000mA current draw,
so roughly 250mA @ 2.95V would be 738mW.
If the fan was drawing 100mA @ 3V it would use 300mW.
So these particular solar lights should have heaps of capacity.
As far as the voltage is concerned, an LM2596 regulator module could look after that & allow the fan to be set as desired.
Assuming the batteries are in parallel, their output would be above 3.6V, & these regs could efficiently deliver the 2V that you mention.
[ You are not allowed to view attachments ]
Cheers
Phil.