Simple Q&A D&D 3.5 (by RAW) XXI

[Duke of Urrel]

Q 1121

From Sleep-spell:
"Awakening a creature is a standard action (an application of the aid another action). "

How close do you have to be?

A 1121

I believe it's a safe assumption that you must be close enough to hit the creature you want to awaken with a mêlée attack – though of course you don't have to inflict any damage with this "attack." This follows both from the description of the Sleep spell, which states that "slapping or wounding" a sleeper ends the spell's effect, and from the fact that the success of the Aid Another action is determined by a simple mêlée attack that inflicts no damage.

We can also offer the argument that the Sleep spell would never be very effective in combat if mere noise, such as a shout from 30 feet away, were sufficient to break the spell.

The only difference between the ordinary use of the Aid Another action and the act of awakening a sleeping creature is that in the former case, you must generally be within reach of an enemy, whereas in the latter case, you must generally be within reach of a comrade.