Texas Cucumber (banana squash; hot pepper; watermelon)

There is no standard slang definition for “Texas cucumber.” The term has been used to describe banana squash, hot pepper, and a large watermelon.
 
 
Viceland.com
Chin tricked me into eating a hot pepper. “Texas cucumber.” It was fucking intense pain for about 20 minutes. 

17 September 1958, San Mateo (CA) Times, pg. 35:
RODEO, Calif.—California bar manager Jake Fisher is exhibiting a 98-pound watermelon a friend brought from Oklahoma. He calls it a “Texas cucumber.”
   
30 October 1962, Middlesboro (KY) Daily News, pg. 5:
Rev. Evans issued a challenge to the students by shucking some beautiful Indian corn, and offering free seed and prizes for next year’s best. He also displayed a banana squash, which he called a “Texas cucumber.”