What do you mean by "best"?
Biggest fish? Look for stocked (bleh) fish on eastern sierra lakes…
Most fish? Look for overcrowded lakes plugged with malnourished brookies…. plenty of those around….
Bizzarre crossbreeds in alpine solitude? Plenty of that too…
or just head out into the back country… I've caught 18" trout in sluggish meadow creeks that were 12" wide and 4" deep…..
There are so many great places holding fish in the sierras that's it's simply absurd. If you go on a short 3 day trip likely you'll pass dozens of amazing creeks and rivers.
An easy suggestion:
The ENTIRE kern river drainage…
beyind that, a little more info on what exactly you're looking for and we can help..
For me it's always been that special blend of crazy native crossbreeds in a gorgeous setting with nobody around that are chewing the paint off of anything I throw at them that works… But that's just me…