This is the 8436th most frequent Russian word.
напьешься
"Напьешься" means "you will get drunk" or "you will drink enough" in English, depending on context.
напьешься is used here in the sense of drinking to a state of being satiated.
Если ты выпьешь столько воды за один раз, ты точно напьешься.
If you drink so much water at once, you will definitely drink yourself full.
напьешься refers to the act of becoming intoxicated from consuming alcoholic drinks.
На вечеринке он сказал, что напьешься быстро, если пить крепкий алкоголь.
At the party, he said you'll get drunk quickly if you drink strong alcohol.
напьешься is implied to mean consuming an adequate amount of water to replenish and feel refreshed.