yes, we have done it, in fact we originally hoped we could get away with a heatsink but it would have to be so big that we finally opted for a fan.
If you are not in a hurry, you can affix a heatsink (we used 30mm x 20mm x 6mm) using heat-conductive epoxy glue.
You will quickly overheat under high load (e.g., tensorflow). But you could reduce the CPU frequency using parameter cpumax documented here: http://jevois.org/doc/UserCli.html
setpar cpumax 600
will cap you to 600Mhz, You should be able to run heavy loads without overheating at that speed. In fact the RPi slows down to 600MHz when it overheats and has no fan.