Nerve fibers innervating sweat glands release the following at their endings

Sweat glands are innervated by cholinergic nerve fibres. Those fibres that secrete acetylcholine are said to be cholinergic. All preganglionic neurons are cholinergic in both the sympathetic and the parasympathetic nervous systems. Acetylcholine and acetylcholine-like substances, when applied to the ganglia, will excite both sympathetic and parasympathetic postganglionic neurons. Either all or almost all of the postganglionic neurons of the parasympathetic system are also cholinergic. Conversely, most of the postganglionic sympathetic neurons are adrenergic. However, the postganglionic sympathetic nerve fibres to the sweat glands are cholinergic.  Thus, the terminal nerve endings of the parasympathetic system all or virtually all secrete acetylcholine. These neurotransmitters in turn act on different organs to cause respective parasympathetic or sympathetic effects. Therefore, acetylcholine is called a parasympathetic transmitter.