you can, if you are lucky.
Flash drives are not working correctly, if not at all, with Wii/vWii/WiiU homebrew.
some are working in read mode only, some are not working at all.
write mode will most likely crash/freeze the homebrew, and at worse even corrupt your data on the flash.
you'd probably have better chance with an old product, new ones seems to have lot of issues.
if you care about the data on it, or don't have time to waste trying to make it work on the console, don't use flash.
if you want to try anyway, be sure the data are not important, and you have backups.