The sentence that correctly follows punctuation conventions is:
Many customers have asked, “Does milk from grass-fed cows taste better?”
The other sentences have punctuation or grammatical issues:
- "The state’s most popular ice cream shop is in Boulder Colorado." should include a comma: "The state’s most popular ice cream shop is in Boulder, Colorado."
- "Although the creamery uses dairy from many producers; it sources it’s eggs from one farm." should use "its" instead of "it’s" (which is a contraction for "it is"), and should use a comma instead of a semicolon: "Although the creamery uses dairy from many producers, it sources its eggs from one farm."
- "However the ice cream has very few ingredients." should include a comma after "However": "However, the ice cream has very few ingredients."