Daniel Courtney was playing tennis at David Lloyd in Bracknell before he realised his work van was broken into.
The Bracknell man noticed a dent in the handle and when he looked inside, over £5,000 in specialist equipment was gone.
Currently, Daniel is out of work as he is self-employed and relies on the tools for his job.
His sister, Sherrie Bennet said he is "devastated that this has happened because he is very vigilant about where he parks his van.
"He now can't work unfortunately, David Lloyd has no CCTV and I find this awful considering the amount of membership fees people pay.
"He will never get the full amount of money back on his tools that he accumulated over the years and he feels deeply disraught that this van has been targeted."