Answer by taking a quote from the following article:

Sugarland is an American country music duo consisting of singer-songwriters Jennifer Nettles (lead vocals) and Kristian Bush (vocals, acoustic guitar, mandolin). Sugarland was founded in 2002 by Kristen Hall with Bush and became a trio after hiring Jennifer Nettles. Signed to Mercury Nashville Records in 2004, Sugarland broke through that year with the release of their debut single "Baby Girl", the first single from their multi-platinum debut album Twice the Speed of Life.

Sugarland's Jennifer Nettles paired with Pepsi Max and recorded a commercial for Super Bowl XLVI. Nettles recorded Hank Williams' "Your Cheatin' Heart" which is featured in the commercial as a Coke Zero delivery man tries to buy a Pepsi Max without being discovered.  Sugarland recorded a song for the 2012 movie, Act of Valor. The soundtrack to the movie was released on February 21, 2012. The song is titled "Guide You Home". Kristian Bush confirmed in late January that Sugarland will be touring in "mid to late Spring" and that they're "going to source our fans for our set list." On April 5, 2012, the duo commenced their fourth headlining tour: In Your Hands tour 2012. On June 18, it was announced that Nettles was pregnant and due in November, two months after their summer tour concluded. Her son, Magnus Hamilton Miller, was born on December 6, 2012.  With Nettles on maternity leave, Bush made his solo debut in March 2013 at the inaugural C2C: Country to Country Festival at the O2 Arena in London, England; his first song release as a solo act, "Love or Money," debuted on iTunes in Europe the following week. He often takes part in the Country Music Association's Songwriters Series, which has included various appearances across the United States, as well as time spent abroad with the CMA's first-ever international initiative showcasing Nashville songwriters and their work to foreign audiences in clubs and theaters.  In August 2013, Nettles released a solo single, "That Girl", for Mercury. It is the lead single to her solo album of the same name, released on January 14, 2014 via Mercury Nashville. Rick Rubin produced the album. Her second album Playing with Fire was released in 2016 and, like Bush did in 2013, Nettles played the 2017 C2C: Country to Country Festival.  In 2014, Bush signed to producer Byron Gallimore's Streamsound Records as a solo artist. His debut solo single, "Trailer Hitch," was released to radio and retailers on July 28, 2014. His debut solo album, Southern Gravity, was released on April 7, 2015. He wrote 300 songs for the project, which he refers to as a "mainstream country record that is meant to be played on the radio." Nettles released two solo albums in 2016, Playing with Fire on May 13, and To Celebrate Christmas on October 28.

Did Bush release any singles while he was solo?
His debut solo single, "Trailer Hitch," was released to radio and retailers on July 28, 2014.