This is a short one!
I've recently discovered the Rhythm Randomizer at https://www.rhythmrandomizer.com
It is an excellent way to practice rhythms, which I think should be very useful for Sight-reading practice.
My suggested settings are:
Then probably 4 bars (measures here, I think it's an American site), pick a time signature, and then choose a few rhythm patterns to practice. I'd start by practicing each group, then pick a few which are causing trouble to repeat over and over again!
I'd start by clapping the pulse as the computer plays the rhythm, then clap the rhythm while the computer acts as metronome. If that works well, try stepping the pulse and clapping the rhythm at the same time!
See how many complicated rhythms you can get correct. There's no substitute for practice!