The men's world record is 9.58 seconds, set by Jamaica's Usain Bolt in 2009, while the women's world record is 10.49 seconds, set by American Florence Griffith-Joyner in 1988[a].
[0] https://en.wikipedia.org/wiki/100_metres [a] is a footnote on the wikipedia page, discussing the validity of the record due to wind speed measurement concerns; read the page and footnote if you care about that level of detail
You'd need to persuade someone already at a pretty elite level to take part though. Maybe someone who just did their last Olympics?
The one extreme option out there is surgery to change the attachment point of the tendon to the bone, generating more torque from the same contractile force. Some possibly acropyphal rumors claim lifters in nations with very unscrupulous doctors may have done that when the opportunity presented itself because of an incidental muscle tear.
The other big thing on the horizon is gene doping, such as with Myostatin in Bully Whippets.