Easy to be imposed on, or taken in; also expert, dexterous clever. Sweet’s your hand; said of one dexterous at stealing.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Sweating * Sweet HeartNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes