Depending on personal preference, it is either an expression of joy, happiness or delight or an expression of sarcasm in response to a small gain/reward etc.
Joy.
"You got an A+ on your maths test!"
"Goody gumdrops!"
Sarcasm.
"For finding the cure for cancer, we give you this small keychain."
"Oh, Goody gumdrops"
A trip to a grocery store, convenience store, or gas station for the sole purpose of buying an excessive amount of junk food and sugary drinks, usually with friends. A chud run often happens late at night and ends with everyone involved hating themselves afterwards.