Not exactly WordPress related, but here's a short example using a find with a directory type and zero maxdepth:

$ find /srv/users/serverpilot/apps/*/public/ \
-type d \
-maxdepth 0 \
-exec /usr/local/bin/wp core update --path={} \;

or in a single line:

$ find /srv/users/serverpilot/apps/*/public/ -type d -maxdepth 0 -exec /usr/local/bin/wp core update --path={} \;

Here's an example using find with a directory type and zero maxdepth:

$ find /srv/users/serverpilot/apps/*/public/ \
-type d \
-maxdepth 0 \
-exec /usr/local/bin/wp core update --path={} \;

or in a single line:

$ find /srv/users/serverpilot/apps/*/public/ -type d -maxdepth 0 -exec /usr/local/bin/wp core update --path={} \;