Perhaps a certain interpretation of the RAW could lead to the conclusion that these could be used together…
How many other DMs here would actually allow this?
The RAW doesn’t explicitly state that it CAN be done, but since it also doesn’t explicitly state that it CANNOT be done, some are assuming they should be able too. This is a situation where conceptual logic should be used to determine a ruling where none is specifically written…
These are two opposing concepts.
-A touch attack (usually) requires a lower attack roll because it doesn’t matter where you strike your target.
-A sneak attack does extra damage because the character is targeting a specific (vital) part of the target.
If using a spell/attack that normally requires only a touch-attack, I would allow an attack roll vs. the targets normal (or flat-footed) AC if the character wants to apply sneak attack damage. Otherwise, he/she can make the touch-attack roll and do normal damage (per the spell, etc).