What's the range of touch attacks when using the Spell Sniper Feat? Is it 10ft or 30ft as with the sorcerer meta feat that doubles range?
It has no effect. The range is still "touch"
The range of "touch" is not number, so doubling touch would be like "two hand touch" or something silly.
Point being, touch is not a numerical range and as such cannot be doubled.
if you had a feat or spell or other ability to increase your natural reach you would be able to cast touch spells at further distances, but this feat does nothing to extend your reach, just the range of spells with numerical values.
In the case of the sorcerer meta magic power "Distant Spell", it specifically gives a range to touch attacks (30'), that would be doubled to 60' with this feat.