  In our previous work, we investigated the occurrence rate of super-flares on
various types of stars and their statistical properties, with a particular
focus on G-type dwarfs, using entire Kepler data. The said study also
considered how the statistics change with stellar rotation period, which in
turn, had to be determined. Using such new data, as a by-product, we found 138
Kepler IDs of F and G types main sequence stars with rotation periods less than
a day ($P_{\rm rot}<1$ d). On one hand, previous studies have revealed short
activity cycles in F-type and G-type stars and the question investigated was
whether or not short-term activity cycles are a common phenomenon in these
stars. On the other hand, extensive studies exist which establish empirical
connection between a star's activity cycle and rotation periods. In this study,
we compile all available Kepler data with $P_{\rm rot}<1$ d, derive and use,
established empirical relation between $P_{\rm cyc}$ and $P_{\rm rot}$ with the
aim to provide predictions for very short $5.09\leq P_{\rm cyc}\leq 38.46$ d
cases in a tabular form. We propose an observation to measure $P_{\rm cyc}$
using monitoring program of stellar activity (e.g. activity-related
chromospheric emission S-index) or similar means for the Kepler IDs found in
this study in order put to test the derived here empirical relations between
$P_{\rm cyc}$ and $P_{\rm rot}$. We also propose an alternative method for
measuring very short $P_{\rm cyc}$, using flare-detection algorithms applied to
future space mission data.
