Trainers » Rare Candy
Can I use Rare Candy on a Pokémon that has already evolved normally that turn?
No you cannot, because Rare Candy can only evolve Basic Pokémon If you evolved a Pokémon already this turn, it would not be a Basic any more.
Source: PUI Rules Team (2003-10-23)

Relevant cards

Note: All applicable cards may not be listed below.
BW10_105
BW10_85
BW5_100
DP4_102
EX13_90
EX2_88
EX9_83
HGSS2_82
POP5_7
POP8_10
SM1_129
SM2_165
SM7_142
SWSH1_180
SWSH1_180
XY5_135