Mod Features:

Forgetting to sleep for days will afflict you with Drowsy which will give you a litany of tiny debuffs which can stack up to 10 times as you continue to not sleep.
Sleeping regularly on the other hand will give you Invigorated which gives you small buffs.
The stats that are increased/reduced by the effects are: Movement Speed, Knockback Resistance, Attack Damage, XP Gain, and Mining Speed
Drowsy may be staved off for a while with a cookie, coffee, or tea

Detailed Breakdown:

You will become Drowsy after a full day without sleep. You also have 1 day of leniency by default. So 2 days of no sleep to become Drowsy by default.
Drowsy will reduce base Movement Speed by 3.75% per level.
Drowsy will reduce base Knockback Resistance by 5% per level.
Drowsy will reduce total Attack Damage by 5% per level.
Drowsy will reduce XP Gain by 7.5% per level.
Drowsy will reduce mining speed by 4% per level.
Drowsy will scale up by one for each day you continue to not sleep. Drowsy will scale up to level 10.
Any food with the word "cookie", "coffee", or "tea" will remove the Drowsy effect. If you do this as soon as you get the effect, you can stave off Drowsy for ~1 hour real time.

You will become Invigorated after you wake up if you had gone to sleep the night before.

Invigorated will increase base Movement Speed by 4% per level.
Invigorated will increase base Knockback Resistance by 2% per level.
Invigorated will increase total Attack Damage by 4% per level.
Invigorated will increase XP Gain by 5% per level.
Invigorated will increase mining speed by 4% per level.
Invigorated will scale up by one for each day you continue to regularly sleep. Invigorated will scale up to level 5.

Recommended Together:

Drowsy+Phantoms of The End together try to do what phantoms were meant to do with a smoother player experience without getting rid of the phantoms. The mod Phantoms of the End gets rid of the regular annoying and inconsistent phantom attacks and instead moves them to the end where they can be found uncommonly in certain end biomes. It also makes large groups of phantoms patrol end cities, which introduces new threats and a new experience of raiding end cities and might stop players from rushing the ship every time. Drowsy afflicts you with a variety of tiny debuffs the more you stay awake, which can be ignored for a couple of days but will scale up to be debilitating if you never sleep. And, instead of only a disincentive, there is now also an incentive to sleep. You will gain Invigorated after regularly sleeping which give some minor buffs.

Drowsy + Phantoms of The End

https://www.curseforge.com/minecraft/mc-mods/drowsy https://www.curseforge.com/minecraft/mc-mods/phantoms-of-the-end

Gives buffs and debuffs based on sleep. Stop regular phantom spawns. Move them to end biomes and end cities.